While most of our patients are aware that sunbathing has an adverse impact on their skin’s health and appearance, many are unaware how much incidental sun exposure they receive during the day. Running errands, walking the dog, and even driving the car, they are unintentionally accumulating a significant amount of ultraviolet (UV) exposure.
As you know, incidental exposure begins in childhood and quickly accumulates. While most patients understand our recommendations to use sunscreen when they’re going to spend time in the sun, many people assume they need photoprotection only when they expect to be in the sun for long periods. They also underestimate the cumulative UV dosage from incidental daily exposures. In addition, many of our patients don’t understand the need to incorporate sunscreen application into their morning skincare regimens to help protect them against these small, unintentional UV doses.
However, some patients are getting the important sunscreen message. According to the Skin Cancer Foundation, fewer than 33% of Americans of all ages use sunscreen.1 According to a recent survey of sunscreen use in more than 10,000 adolescents across the nation, only 40% of girls 12 to 18 years of age and 26% of boys use sunscreen.2
Yet, even when they do heed the message to use sunscreen, they often don’t use an amount great enough to offer full protection. While it is recommended that patients use the equivalent of 2 ounces of sunscreen to cover their bodies, most individuals use less.
This results in sunscreen users receiving only 25% to 50% of the sun protection factor (SPF) that they thought they were getting.3,4 Also, conventional sunscreens provide incomplete protection from UV-induced oxidative damage and inflammation, which repeatedly have been shown to contribute to photoaging, independently of UV.5,6
Add up all of these pitfalls, and it’s easy to see why even patients who say they are using sunscreens may have a false sense of security.
Increasing the Amount of Protection Offered by Sunscreens
Adding topical and oral anti-oxidants to sunscreens augments the level of photoprotection offered by the sunscreen and adds to the body’s anti-oxidant reservoir to protect against oxidative stress and inflammation.5 The skin relies on endogenous anti-oxidants to protect it from oxidative stress caused by sunlight and pollution. The physiologic anti-oxidant reservoir comprises vitamins C and E, glutathione and ubiquinone.5 Plants, too, have to protect themselves from the relentless onslaught of UVR, and so have their own anti-oxidants.
Unlike synthetic agents, which have a relatively narrow spectrum of activity, botanical anti-oxidants belong to several different chemical classes and may be active in more than one pathway involved in photodamage.6 Many active natural ingredients are added to sunscreens to enhance photoprotection and to improve their cosmetic elegance. To emphasize a point: These natural ingredients are not used as stand-alones but rather in conjunction with chemical and physical sunscreens. It is important for dermatologists to become familiar with the science underlying these botanical agents and to be able to discuss them with patients who may be aware of them via product advertising and the Internet.
Topical Botanical Anti-oxidants
Feverfew is a flower that has been used in folk medicine for more than 2,000 years to treat headache and fever. Its efficacy in these conditions was attributed to parthenolide compounds that are known skin irritants. Recently, a purified extract of feverfew (Feverfew PFE) was shown to have strong anti-inflammatory and anti-oxidant activity without skin sensitization.7 In clinical trials, Feverfew PFE was shown to prevent UV-induced erythema.
Figure 1 shows cross-polarized images of the forearm of a patient treated for 2 days with a 1% extract of Feverfew PFE and placebo and then exposed to 2x the minimal erythema dose (MED) of UVB. It’s evident that the areas treated with Feverfew PFE were significantly less red than the placebo-treated skin at both 24 and 48 hours after UVB exposure. This finding also was corroborated via chromametry and diffuse reflectance spectroscopy.8
Green tea contains a number of polyphenols, the most active in skin being (-)-epigallocatechin-3-gallate (EGCG).9 Similar to Feverfew PFE, EGCG extracts in varying concentrations can block the erythemic response to 2x MED of solar-simulated radiation in a dose-related manner up to 72 hours post-application. Significantly, EGCG pretreatment resulted in a 58% reconstitution of Langerhans cells, suggesting that it is capable of mitigating UV-induced immunosuppression. EGCG does not appear to act as a conventional sunscreen, as it did not absorb any spectra of UV light correlated with photodamage.10
Vitamins C and E are endogenous antioxidants. Ferulic acid (FA) is a plant anti-oxidant. A recent study demonstrated the ability of ferulic acid to stabilize vitamins C and E in solution. In the same study, this combination of 15% L-ascorbic acid, 1% a-tocopherol and 0.5% ferulic acid applied daily for 4 days provided virtually complete protection against erythema resulting from 2x to 10x MED solar-simulated UVR.11
Tamarind pods and seeds are frequently used in Asian cuisine and contain oligosaccharins — complex carbohydrates found in plants. In one study, tamarind polysaccharide at dosages of 100 ng/ml and 10 µg/ml had an approximate SPF of 1, but it protected the skin from UV-induced loss of Langerhans cells following UVR.12 Nickel-allergic subjects treated with a low dose of tamarind had normal contact hypersensitivity responses to nickel at irradiated sites. These findings suggest that the addition of tamarind or other plant oligosaccharins to sunscreens may be capable of counteracting UV-induced immunosuppression.
Turmeric is a curry powder component that is widely used in Asia for medicinal purposes including as a topical burn treatment. Its major component, curcumin, has been shown to protect the skin after exposure to radiation or during radiotherapy. It appears to act similarly to COX-2.13 Low doses of curcumin have been found to mediate tumor promotion in mouse skin by 12-O-tetradecanoylphorbol-13-acetate (TPA).14 Because of its strong odor and yellow color, it is best used in dermatology as an oral agent. However, the body of research demonstrating its anti-carcinogenic and anti-inflammatory activities is impressive.15
Table 1 lists some of the other topical botanicals that are being studied for their contributions to the prevention or repair of photodamage.16-20
Oral Photoprotection
In addition to the free-radical-quenching activity of the topical antioxidants discussed above, there is evidence that certain oral agents also are photoprotective, including turmeric15 and green tea.9
Recently, the Central American fern, Polypodium leucotomos (PL), administered orally, has been shown to be an effective photoprotective agent. Nine subjects with Fitzpatrick skin phototypes II and III were exposed to 2x to 3x MED of solar-simulated light after ingestion of an extract of PL (dosage 7.5 mg/kg). One day later, subjects received a second dose of PL and were again exposed to the simulated UV at 5 different time points from 30 minutes to 3 hours following dosing. PL-treated skin showed significantly less (P<0.01) erythema at 24 hours post-UVR than did untreated skin. Differences in erythema between PL-treated and non-PL-treated skin were statistically significant up to 2 hours after PL ingestion. PL-treated skin also had significantly fewer sunburn cells (P<0.05), cyclobutane pyrimidine dimers (P<0.001), and proliferating epidermal cells (P<0.001) and significantly less dermal mass cell infiltration (P<0.05). There was a trend toward preservation of Langerhans cells and reduced vasodilation.21
Repair of Cutaneous Signs of Photodamage
The anti-oxidant and anti-inflammatory activities of the botanical agents discussed above are capable of reducing the erythema and inflammation that are the immediate results of UV exposure. Over the long term, however, skin that has been chronically exposed to UV shows predictable changes, including pigmentary abnormalities, fine lines and wrinkles, and dryness.
Animal studies have shown that topical soy is capable of lightening hyperpigmentation by means of its interaction with the protease-activated receptor-2 (PAR-2) pathway, which inhibits melanosome transfer from melanocytes to keratinocytes.22 A later clinical study showed that topical application of stabilized total soy extracts reduced the hyperpigmentation associated with several hyperpigmentation disorders including solar lentigines, melasma and post-inflammatory hyperpigmentation.23 In vitro studies also demonstrated the ability of total soy to stimulate collagen synthesis in normal human dermal fibroblasts and to increase elastin formation at the upper portion of the dermis. The increase in fine and highly branched elastin fibers resembled the type of “repair zone” that is seen when UV-damaged skin is treated with retinoids.24
Daily Care of Photodamaged Skin
Photodamage leads to disruption of the epidermal barrier, resulting in inflammation, hyperplasia, abnormal
keratinization, dryness and the formation of an inferior stratum corneum.25 Therefore, photodamaged skin requires gentle cleansing and moisturizing with agents that are capable of aiding in the restoration of a normal epidermal barrier.
Colloidal oatmeal is one of the few natural ingredients to be recognized by the U.S. Food and Drug Administration as a skin protectant. Oat b-glucan is a water-soluble, high-molecular-weight polysaccharide that can protect and restore the epidermal barrier. Because it is hydrophilic, it binds water to the skin and therefore helps hydrate it. Colloidal oatmeal, which contains proteins, sugars, phenolics, flavonoids, saponins and UV absorbers, has been shown in vitro to reduce UV-associated redness and skin irritation.26
Lipids help to repair and maintain this barrier. Saponins contained in colloidal oatmeal help solubilize dirt and sebum, thus providing extremely gentle cleansing. There are a wide variety of skincare products containing various oat components, and they are particularly appropriate for caring for skin that has sustained UV and other environmental damage.
Promising New Approach
It is increasingly clear that brief incidental sun exposures that occur during the activities of daily living add significantly to the average individual’s daily UV exposure. Cumulative oxidative stress leading to inflammation is increasingly implicated as an important factor in UV-related cutaneous damage. In addition to physical and chemical sunscreens to block and absorb UV radiation, enhancement of the body’s natural anti-oxidant reservoir is also needed to increase the level of photoprotection.
A variety of botanicals are currently under study for their ability to augment the photoprotection provided by conventional sunscreens. Botanical compounds typically have a broad spectrum of relevant activities, including free radical quenching and blocking of inflammation. The addition of botanicals to sunscreens is a promising new approach for reducing UV-mediated photodamage and skin aging.
While most of our patients are aware that sunbathing has an adverse impact on their skin’s health and appearance, many are unaware how much incidental sun exposure they receive during the day. Running errands, walking the dog, and even driving the car, they are unintentionally accumulating a significant amount of ultraviolet (UV) exposure.
As you know, incidental exposure begins in childhood and quickly accumulates. While most patients understand our recommendations to use sunscreen when they’re going to spend time in the sun, many people assume they need photoprotection only when they expect to be in the sun for long periods. They also underestimate the cumulative UV dosage from incidental daily exposures. In addition, many of our patients don’t understand the need to incorporate sunscreen application into their morning skincare regimens to help protect them against these small, unintentional UV doses.
However, some patients are getting the important sunscreen message. According to the Skin Cancer Foundation, fewer than 33% of Americans of all ages use sunscreen.1 According to a recent survey of sunscreen use in more than 10,000 adolescents across the nation, only 40% of girls 12 to 18 years of age and 26% of boys use sunscreen.2
Yet, even when they do heed the message to use sunscreen, they often don’t use an amount great enough to offer full protection. While it is recommended that patients use the equivalent of 2 ounces of sunscreen to cover their bodies, most individuals use less.
This results in sunscreen users receiving only 25% to 50% of the sun protection factor (SPF) that they thought they were getting.3,4 Also, conventional sunscreens provide incomplete protection from UV-induced oxidative damage and inflammation, which repeatedly have been shown to contribute to photoaging, independently of UV.5,6
Add up all of these pitfalls, and it’s easy to see why even patients who say they are using sunscreens may have a false sense of security.
Increasing the Amount of Protection Offered by Sunscreens
Adding topical and oral anti-oxidants to sunscreens augments the level of photoprotection offered by the sunscreen and adds to the body’s anti-oxidant reservoir to protect against oxidative stress and inflammation.5 The skin relies on endogenous anti-oxidants to protect it from oxidative stress caused by sunlight and pollution. The physiologic anti-oxidant reservoir comprises vitamins C and E, glutathione and ubiquinone.5 Plants, too, have to protect themselves from the relentless onslaught of UVR, and so have their own anti-oxidants.
Unlike synthetic agents, which have a relatively narrow spectrum of activity, botanical anti-oxidants belong to several different chemical classes and may be active in more than one pathway involved in photodamage.6 Many active natural ingredients are added to sunscreens to enhance photoprotection and to improve their cosmetic elegance. To emphasize a point: These natural ingredients are not used as stand-alones but rather in conjunction with chemical and physical sunscreens. It is important for dermatologists to become familiar with the science underlying these botanical agents and to be able to discuss them with patients who may be aware of them via product advertising and the Internet.
Topical Botanical Anti-oxidants
Feverfew is a flower that has been used in folk medicine for more than 2,000 years to treat headache and fever. Its efficacy in these conditions was attributed to parthenolide compounds that are known skin irritants. Recently, a purified extract of feverfew (Feverfew PFE) was shown to have strong anti-inflammatory and anti-oxidant activity without skin sensitization.7 In clinical trials, Feverfew PFE was shown to prevent UV-induced erythema.
Figure 1 shows cross-polarized images of the forearm of a patient treated for 2 days with a 1% extract of Feverfew PFE and placebo and then exposed to 2x the minimal erythema dose (MED) of UVB. It’s evident that the areas treated with Feverfew PFE were significantly less red than the placebo-treated skin at both 24 and 48 hours after UVB exposure. This finding also was corroborated via chromametry and diffuse reflectance spectroscopy.8
Green tea contains a number of polyphenols, the most active in skin being (-)-epigallocatechin-3-gallate (EGCG).9 Similar to Feverfew PFE, EGCG extracts in varying concentrations can block the erythemic response to 2x MED of solar-simulated radiation in a dose-related manner up to 72 hours post-application. Significantly, EGCG pretreatment resulted in a 58% reconstitution of Langerhans cells, suggesting that it is capable of mitigating UV-induced immunosuppression. EGCG does not appear to act as a conventional sunscreen, as it did not absorb any spectra of UV light correlated with photodamage.10
Vitamins C and E are endogenous antioxidants. Ferulic acid (FA) is a plant anti-oxidant. A recent study demonstrated the ability of ferulic acid to stabilize vitamins C and E in solution. In the same study, this combination of 15% L-ascorbic acid, 1% a-tocopherol and 0.5% ferulic acid applied daily for 4 days provided virtually complete protection against erythema resulting from 2x to 10x MED solar-simulated UVR.11
Tamarind pods and seeds are frequently used in Asian cuisine and contain oligosaccharins — complex carbohydrates found in plants. In one study, tamarind polysaccharide at dosages of 100 ng/ml and 10 µg/ml had an approximate SPF of 1, but it protected the skin from UV-induced loss of Langerhans cells following UVR.12 Nickel-allergic subjects treated with a low dose of tamarind had normal contact hypersensitivity responses to nickel at irradiated sites. These findings suggest that the addition of tamarind or other plant oligosaccharins to sunscreens may be capable of counteracting UV-induced immunosuppression.
Turmeric is a curry powder component that is widely used in Asia for medicinal purposes including as a topical burn treatment. Its major component, curcumin, has been shown to protect the skin after exposure to radiation or during radiotherapy. It appears to act similarly to COX-2.13 Low doses of curcumin have been found to mediate tumor promotion in mouse skin by 12-O-tetradecanoylphorbol-13-acetate (TPA).14 Because of its strong odor and yellow color, it is best used in dermatology as an oral agent. However, the body of research demonstrating its anti-carcinogenic and anti-inflammatory activities is impressive.15
Table 1 lists some of the other topical botanicals that are being studied for their contributions to the prevention or repair of photodamage.16-20
Oral Photoprotection
In addition to the free-radical-quenching activity of the topical antioxidants discussed above, there is evidence that certain oral agents also are photoprotective, including turmeric15 and green tea.9
Recently, the Central American fern, Polypodium leucotomos (PL), administered orally, has been shown to be an effective photoprotective agent. Nine subjects with Fitzpatrick skin phototypes II and III were exposed to 2x to 3x MED of solar-simulated light after ingestion of an extract of PL (dosage 7.5 mg/kg). One day later, subjects received a second dose of PL and were again exposed to the simulated UV at 5 different time points from 30 minutes to 3 hours following dosing. PL-treated skin showed significantly less (P<0.01) erythema at 24 hours post-UVR than did untreated skin. Differences in erythema between PL-treated and non-PL-treated skin were statistically significant up to 2 hours after PL ingestion. PL-treated skin also had significantly fewer sunburn cells (P<0.05), cyclobutane pyrimidine dimers (P<0.001), and proliferating epidermal cells (P<0.001) and significantly less dermal mass cell infiltration (P<0.05). There was a trend toward preservation of Langerhans cells and reduced vasodilation.21
Repair of Cutaneous Signs of Photodamage
The anti-oxidant and anti-inflammatory activities of the botanical agents discussed above are capable of reducing the erythema and inflammation that are the immediate results of UV exposure. Over the long term, however, skin that has been chronically exposed to UV shows predictable changes, including pigmentary abnormalities, fine lines and wrinkles, and dryness.
Animal studies have shown that topical soy is capable of lightening hyperpigmentation by means of its interaction with the protease-activated receptor-2 (PAR-2) pathway, which inhibits melanosome transfer from melanocytes to keratinocytes.22 A later clinical study showed that topical application of stabilized total soy extracts reduced the hyperpigmentation associated with several hyperpigmentation disorders including solar lentigines, melasma and post-inflammatory hyperpigmentation.23 In vitro studies also demonstrated the ability of total soy to stimulate collagen synthesis in normal human dermal fibroblasts and to increase elastin formation at the upper portion of the dermis. The increase in fine and highly branched elastin fibers resembled the type of “repair zone” that is seen when UV-damaged skin is treated with retinoids.24
Daily Care of Photodamaged Skin
Photodamage leads to disruption of the epidermal barrier, resulting in inflammation, hyperplasia, abnormal
keratinization, dryness and the formation of an inferior stratum corneum.25 Therefore, photodamaged skin requires gentle cleansing and moisturizing with agents that are capable of aiding in the restoration of a normal epidermal barrier.
Colloidal oatmeal is one of the few natural ingredients to be recognized by the U.S. Food and Drug Administration as a skin protectant. Oat b-glucan is a water-soluble, high-molecular-weight polysaccharide that can protect and restore the epidermal barrier. Because it is hydrophilic, it binds water to the skin and therefore helps hydrate it. Colloidal oatmeal, which contains proteins, sugars, phenolics, flavonoids, saponins and UV absorbers, has been shown in vitro to reduce UV-associated redness and skin irritation.26
Lipids help to repair and maintain this barrier. Saponins contained in colloidal oatmeal help solubilize dirt and sebum, thus providing extremely gentle cleansing. There are a wide variety of skincare products containing various oat components, and they are particularly appropriate for caring for skin that has sustained UV and other environmental damage.
Promising New Approach
It is increasingly clear that brief incidental sun exposures that occur during the activities of daily living add significantly to the average individual’s daily UV exposure. Cumulative oxidative stress leading to inflammation is increasingly implicated as an important factor in UV-related cutaneous damage. In addition to physical and chemical sunscreens to block and absorb UV radiation, enhancement of the body’s natural anti-oxidant reservoir is also needed to increase the level of photoprotection.
A variety of botanicals are currently under study for their ability to augment the photoprotection provided by conventional sunscreens. Botanical compounds typically have a broad spectrum of relevant activities, including free radical quenching and blocking of inflammation. The addition of botanicals to sunscreens is a promising new approach for reducing UV-mediated photodamage and skin aging.
While most of our patients are aware that sunbathing has an adverse impact on their skin’s health and appearance, many are unaware how much incidental sun exposure they receive during the day. Running errands, walking the dog, and even driving the car, they are unintentionally accumulating a significant amount of ultraviolet (UV) exposure.
As you know, incidental exposure begins in childhood and quickly accumulates. While most patients understand our recommendations to use sunscreen when they’re going to spend time in the sun, many people assume they need photoprotection only when they expect to be in the sun for long periods. They also underestimate the cumulative UV dosage from incidental daily exposures. In addition, many of our patients don’t understand the need to incorporate sunscreen application into their morning skincare regimens to help protect them against these small, unintentional UV doses.
However, some patients are getting the important sunscreen message. According to the Skin Cancer Foundation, fewer than 33% of Americans of all ages use sunscreen.1 According to a recent survey of sunscreen use in more than 10,000 adolescents across the nation, only 40% of girls 12 to 18 years of age and 26% of boys use sunscreen.2
Yet, even when they do heed the message to use sunscreen, they often don’t use an amount great enough to offer full protection. While it is recommended that patients use the equivalent of 2 ounces of sunscreen to cover their bodies, most individuals use less.
This results in sunscreen users receiving only 25% to 50% of the sun protection factor (SPF) that they thought they were getting.3,4 Also, conventional sunscreens provide incomplete protection from UV-induced oxidative damage and inflammation, which repeatedly have been shown to contribute to photoaging, independently of UV.5,6
Add up all of these pitfalls, and it’s easy to see why even patients who say they are using sunscreens may have a false sense of security.
Increasing the Amount of Protection Offered by Sunscreens
Adding topical and oral anti-oxidants to sunscreens augments the level of photoprotection offered by the sunscreen and adds to the body’s anti-oxidant reservoir to protect against oxidative stress and inflammation.5 The skin relies on endogenous anti-oxidants to protect it from oxidative stress caused by sunlight and pollution. The physiologic anti-oxidant reservoir comprises vitamins C and E, glutathione and ubiquinone.5 Plants, too, have to protect themselves from the relentless onslaught of UVR, and so have their own anti-oxidants.
Unlike synthetic agents, which have a relatively narrow spectrum of activity, botanical anti-oxidants belong to several different chemical classes and may be active in more than one pathway involved in photodamage.6 Many active natural ingredients are added to sunscreens to enhance photoprotection and to improve their cosmetic elegance. To emphasize a point: These natural ingredients are not used as stand-alones but rather in conjunction with chemical and physical sunscreens. It is important for dermatologists to become familiar with the science underlying these botanical agents and to be able to discuss them with patients who may be aware of them via product advertising and the Internet.
Topical Botanical Anti-oxidants
Feverfew is a flower that has been used in folk medicine for more than 2,000 years to treat headache and fever. Its efficacy in these conditions was attributed to parthenolide compounds that are known skin irritants. Recently, a purified extract of feverfew (Feverfew PFE) was shown to have strong anti-inflammatory and anti-oxidant activity without skin sensitization.7 In clinical trials, Feverfew PFE was shown to prevent UV-induced erythema.
Figure 1 shows cross-polarized images of the forearm of a patient treated for 2 days with a 1% extract of Feverfew PFE and placebo and then exposed to 2x the minimal erythema dose (MED) of UVB. It’s evident that the areas treated with Feverfew PFE were significantly less red than the placebo-treated skin at both 24 and 48 hours after UVB exposure. This finding also was corroborated via chromametry and diffuse reflectance spectroscopy.8
Green tea contains a number of polyphenols, the most active in skin being (-)-epigallocatechin-3-gallate (EGCG).9 Similar to Feverfew PFE, EGCG extracts in varying concentrations can block the erythemic response to 2x MED of solar-simulated radiation in a dose-related manner up to 72 hours post-application. Significantly, EGCG pretreatment resulted in a 58% reconstitution of Langerhans cells, suggesting that it is capable of mitigating UV-induced immunosuppression. EGCG does not appear to act as a conventional sunscreen, as it did not absorb any spectra of UV light correlated with photodamage.10
Vitamins C and E are endogenous antioxidants. Ferulic acid (FA) is a plant anti-oxidant. A recent study demonstrated the ability of ferulic acid to stabilize vitamins C and E in solution. In the same study, this combination of 15% L-ascorbic acid, 1% a-tocopherol and 0.5% ferulic acid applied daily for 4 days provided virtually complete protection against erythema resulting from 2x to 10x MED solar-simulated UVR.11
Tamarind pods and seeds are frequently used in Asian cuisine and contain oligosaccharins — complex carbohydrates found in plants. In one study, tamarind polysaccharide at dosages of 100 ng/ml and 10 µg/ml had an approximate SPF of 1, but it protected the skin from UV-induced loss of Langerhans cells following UVR.12 Nickel-allergic subjects treated with a low dose of tamarind had normal contact hypersensitivity responses to nickel at irradiated sites. These findings suggest that the addition of tamarind or other plant oligosaccharins to sunscreens may be capable of counteracting UV-induced immunosuppression.
Turmeric is a curry powder component that is widely used in Asia for medicinal purposes including as a topical burn treatment. Its major component, curcumin, has been shown to protect the skin after exposure to radiation or during radiotherapy. It appears to act similarly to COX-2.13 Low doses of curcumin have been found to mediate tumor promotion in mouse skin by 12-O-tetradecanoylphorbol-13-acetate (TPA).14 Because of its strong odor and yellow color, it is best used in dermatology as an oral agent. However, the body of research demonstrating its anti-carcinogenic and anti-inflammatory activities is impressive.15
Table 1 lists some of the other topical botanicals that are being studied for their contributions to the prevention or repair of photodamage.16-20
Oral Photoprotection
In addition to the free-radical-quenching activity of the topical antioxidants discussed above, there is evidence that certain oral agents also are photoprotective, including turmeric15 and green tea.9
Recently, the Central American fern, Polypodium leucotomos (PL), administered orally, has been shown to be an effective photoprotective agent. Nine subjects with Fitzpatrick skin phototypes II and III were exposed to 2x to 3x MED of solar-simulated light after ingestion of an extract of PL (dosage 7.5 mg/kg). One day later, subjects received a second dose of PL and were again exposed to the simulated UV at 5 different time points from 30 minutes to 3 hours following dosing. PL-treated skin showed significantly less (P<0.01) erythema at 24 hours post-UVR than did untreated skin. Differences in erythema between PL-treated and non-PL-treated skin were statistically significant up to 2 hours after PL ingestion. PL-treated skin also had significantly fewer sunburn cells (P<0.05), cyclobutane pyrimidine dimers (P<0.001), and proliferating epidermal cells (P<0.001) and significantly less dermal mass cell infiltration (P<0.05). There was a trend toward preservation of Langerhans cells and reduced vasodilation.21
Repair of Cutaneous Signs of Photodamage
The anti-oxidant and anti-inflammatory activities of the botanical agents discussed above are capable of reducing the erythema and inflammation that are the immediate results of UV exposure. Over the long term, however, skin that has been chronically exposed to UV shows predictable changes, including pigmentary abnormalities, fine lines and wrinkles, and dryness.
Animal studies have shown that topical soy is capable of lightening hyperpigmentation by means of its interaction with the protease-activated receptor-2 (PAR-2) pathway, which inhibits melanosome transfer from melanocytes to keratinocytes.22 A later clinical study showed that topical application of stabilized total soy extracts reduced the hyperpigmentation associated with several hyperpigmentation disorders including solar lentigines, melasma and post-inflammatory hyperpigmentation.23 In vitro studies also demonstrated the ability of total soy to stimulate collagen synthesis in normal human dermal fibroblasts and to increase elastin formation at the upper portion of the dermis. The increase in fine and highly branched elastin fibers resembled the type of “repair zone” that is seen when UV-damaged skin is treated with retinoids.24
Daily Care of Photodamaged Skin
Photodamage leads to disruption of the epidermal barrier, resulting in inflammation, hyperplasia, abnormal
keratinization, dryness and the formation of an inferior stratum corneum.25 Therefore, photodamaged skin requires gentle cleansing and moisturizing with agents that are capable of aiding in the restoration of a normal epidermal barrier.
Colloidal oatmeal is one of the few natural ingredients to be recognized by the U.S. Food and Drug Administration as a skin protectant. Oat b-glucan is a water-soluble, high-molecular-weight polysaccharide that can protect and restore the epidermal barrier. Because it is hydrophilic, it binds water to the skin and therefore helps hydrate it. Colloidal oatmeal, which contains proteins, sugars, phenolics, flavonoids, saponins and UV absorbers, has been shown in vitro to reduce UV-associated redness and skin irritation.26
Lipids help to repair and maintain this barrier. Saponins contained in colloidal oatmeal help solubilize dirt and sebum, thus providing extremely gentle cleansing. There are a wide variety of skincare products containing various oat components, and they are particularly appropriate for caring for skin that has sustained UV and other environmental damage.
Promising New Approach
It is increasingly clear that brief incidental sun exposures that occur during the activities of daily living add significantly to the average individual’s daily UV exposure. Cumulative oxidative stress leading to inflammation is increasingly implicated as an important factor in UV-related cutaneous damage. In addition to physical and chemical sunscreens to block and absorb UV radiation, enhancement of the body’s natural anti-oxidant reservoir is also needed to increase the level of photoprotection.
A variety of botanicals are currently under study for their ability to augment the photoprotection provided by conventional sunscreens. Botanical compounds typically have a broad spectrum of relevant activities, including free radical quenching and blocking of inflammation. The addition of botanicals to sunscreens is a promising new approach for reducing UV-mediated photodamage and skin aging.
