Postburn Itch: A Review of the Literature

The problem of postburn itch has been underevaluated and undertreated in the past. However, recently published data have expanded the evidence base, which provides clinicians and their patients with new evaluation and treatment options that can help reduce and potentially eliminate the prolonged distress experienced by burn survivors faced with postburn itch. Although a gold standard evaluation method has not yet been agreed upon, there are a number of tools that have been published that clinicians can use for assessment. Epidemiological evidence has confirmed that the vast majority of both adult and pediatric burn survivors experience itch for years following injury. At discharge from the acute care hospital, 93% of burn survivors with major burn injuries report postburn itch that is still experienced by 44% of adult burn survivors 30 years postburn. Although larger surface area injuries are more likely to require a multimodal treatment approach to reduce the itch intensity as well as the episode duration and frequency, burn survivors with small surface area injuries also experience itch that needs to be addressed. A number of treatment protocols have been described that commonly call for concurrent administration of both pharmacological and nonpharmacological treatment approaches. These protocols provide clinicians with a structured, systematic approach to treatment decisions that are evidence-based. Although many questions require further investigation, the current state of the science creates an ethical imperative that all burn survivors’ itch experience should be quantitatively evaluated and appropriate treatment options explored until satisfactory outcomes are obtained.

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Itch (pruritus) has long been acknowledged as a complication associated with burn injuries and/or donor sites, but in the past many people believed it would spontaneously improve with time. Although the understanding of postburn itch is still evolving, recent evidence has clearly documented that itch can last for years and does not necessarily resolve when the wound has healed. In fact, when asked their opinion, both burn survivors1,2 and burn care professionals1,3 ranked itch as 1 of the top 3 priority issues in need of research and improved treatment options. Thankfully, researchers have responded to this call for more attention; the aim of this review is to present the broadened understanding of the problem and provide updated and evidence-based options for assessment and treatment.

Prevalence 

Historically, the number of burn survivors who experienced itch after their injury had not been well documented; however, recent literature has provided new insights about the prevalence and persistence of this problem. Two recent reports^4,5 from the Burn Model System program (United States) have provided data from large numbers of pediatric and adult burn survivors who sustained major burn injuries. The pediatric burn survivors (n = 430) reported that 93% experienced itch at discharge, 87% at 6 months, 78% at 12 months, and 64% at 24 months following injury. The itch intensity, reported as a mean numeric rating scale (NRS) score, was highest at discharge (5.7/10) and gradually reduced with time (4.3 at 6 months, 3.5 at 12 months, and 2.5 at 24 months).⁴ 

Similarly, the prevalence of itch in the adult burn survivor population (n = 637) was 93% at discharge, 86% at 6 months, 83% at 12 months, and 73% at 24 months.5 These prevalence rates are similar to some reports6-8 but higher than others,^9,10 which may be due in part to the fact that the participants in the Burn Model System program only included those with major burn injuries. It cannot, however, be assumed that small surface area burns do not result in itch since a study of burn survivors with median total body surface area (TBSA) burns of 2% reported that 35% experienced moderate and 14% severe itch that was enough to interfere with sleep and daily activities.¹¹ There does appear to be a portion of the population that never experiences itch.^6,12,13 

Longer term studies have reported that 44% of adult burn survivors continue to experience itch 4 years¹⁴ and 7 years postburn injury.⁵ One study, where the average TBSA burned was 57%, reported that 72% of burn survivors 17 years postburn injury still experienced itch, but survivors more than 30 years postburn had a reduced itch of 44%.¹⁵ A more detailed description was provided on the burn survivors who were 7 years postburn, where it was reported that 76% experienced itch for less than 6 hours per day — 52% rated the intensity as mild and 29% as moderate.⁵ 

For adults, the personal and injury characteristics that were associated with increased itch were younger age,⁵ TBSA burned,^{5,6,9,13,16,17} TBSA grafted,⁵ grafted compared to nongrafted,⁹ time to wound closure,6 number of surgical procedures,7 hypertrophic scar formation,^5,15,16,18 dry skin,⁵ early posttraumatic stress disorder⁷ or psychological factors,^13,19 and female gender.^5,7,16 However, female gender was not consistently associated with itch,¹⁹ and, in some studies, the association changed across time.^7,9 There are mixed findings in the literature about whether skin pigmentation has an impact on itch; Sood et al16 found an increased itch score associated with Asian race but Carrougher et al5 found no significant difference among groups of different racial origins. The face and neck regions were less likely to experience itch as compared with the upper and lower extremities and back or buttocks.^6,9,15 Interestingly, although far fewer investigations have occurred with children, there was no association of itch with any of these characteristics except dry or fragile skin.⁴ 

Unlike many sequelae that burn survivors must deal with after a burn injury, postburn itch can vary substantially with time of day and environmental context. Postburn itch has been reported to occur most often in the afternoon and evening.^10,20 The environmental and physical factors that increase itch are dryness,^10,20 hot environments or warm water,^9,10,20 physical effort,¹⁰ sweating,^9,10,20 and fatigue.²⁰ The factors that were reported to relieve itch were sleep and cold water or cold environments,^10,20 although cold also was reported to provoke itch^9,20 for some 

burn survivors. When asked to select a descriptor that corresponded with their itch, the majority chose bothersome and annoying.¹⁰ In a select group of adult burn survivors who described their itch as frequent and bothersome, 87% experienced itch daily, 96% experienced 3 or more episodes per day, and 52% had episodes lasting from 5 to 30 minutes.²⁰ The itch was reported as unbearable by 94% of those with itch lasting more than 6 months and by 86% of those with itch lasting less than 6 months postburn.²⁰ In a study of 67 consecutive patients, Gauffin et al¹⁰ found some experienced itch every day (59%), some every week (34%), and some every month (9%). One of the important negative consequences of itch in burn survivors is that they can scratch themselves until they bleed (34%), which was associated with trait impulsiveness but was not necessarily associated with those who reported the most intense itch.¹⁰ 

Impact of itch on activities, participation, and quality of life 

When burn survivors who reported severe itch were examined separately, their itch was related to lower health-related quality of life as assessed by the EuroQol 5 dimensions at both 3 and 12 months after injury.¹⁰ An independent relationship between itch and mental distress also was reported for burn survivors with reasonably minor burns (median, 3%) when using the itch scale within the Patient and Observer Scar Assessment Scale and the 36-Item Short Form Survey.¹⁹ In addition, itch positively correlated with difficulty sleeping, which continued to be problematic for those experiencing itch 7 years postburn, with more than 50% continuing to report difficulties with falling asleep.⁵ Falling asleep does appear to be more of an issue for burn survivors with chronic itch; however, 43% of those with acute itch reported requiring sleeping medication, which may have improved their ability to fall asleep²⁰ thereby resulting in an underreporting of the impact of itch. One-third of this population also reported that itch, at least occasionally, affected leisure or social activities, housework or errands, and work or school.⁵ 

In children, there was a moderate positive correlation between itch and pain, sleeping difficulties, fragile skin, and dry skin at different points in time,4 which suggests that at least to some extent these issues are interrelated. 

Thus, itch after a burn injury has now been shown to be a common, persistent, and distressing problem for burn survivors. Although itch is not limited to adults with major burn injuries, it is more likely to be problematic for those who had larger burns that required grafting and particularly those who developed hypertrophic scars. The extremities, back, and buttocks are the most commonly involved anatomical locations. Itch episodes tend to peak in the afternoon or evening and are associated with physical effort or sweating and heat exposure. Particularly for those with severe or chronic itch, the experience is often described as unbearable and has been shown to be related to reduced quality of life. Awareness of the profound impact that itch has on burn survivors’ quality of life demands that health professionals understand, evaluate, and persistently seek out successful treatment options. 

There is substantial debate in the literature about the classification of itch after a burn injury and the pathophysiological basis, particularly of chronic itch.^21-28 Twycross et al²⁹ have proposed 5 different itch categories: cutaneous (pruritoceptive), neuropathic, neurogenic, mixed, and psychogenic. Elevated levels of plasma histamine and increased mast cell numbers have been reported in burn survivors with hypertrophic scars compared with their uninjured skin^8,17,18,30 and have been correlated with postburn itch,^8,18 which supports that there is a cutaneous component. However, the fact that burn survivors commonly only report a partial response to antihistamine medications suggests that the basis for burn-related itch is a mix of cutaneous and neuropathic or neurogenic origins, or possibly also psychogenic.^7,13,19 A number of studies have reported that itch is associated with neuropathic-type symptoms such as pins and needles, electric shocks,⁸ stinging, pinching, and burning,²⁰ which supports that there may be a neuropathic component to postburn itch. Further support for this hypothesis is derived from the fact that for at least a subgroup of burn survivors with intractable itch, their itch was substantially reduced when treated with central acting agents such as naltrexone^31,32 and gabapentin or pregabalin.^33-37 Though recent psychophysiological investigations of chronic postburn itch patients did not support that central sensitization played a major role (in contrast to patients with chronic pain), 85% of the patients reported itch located only, or mainly, in the areas affected by the burn scars.³⁸ Conversely, the therapeutic benefits observed when patients were treated with naltrexone may be related to opioids and their receptors in the peripheral nervous system rather than the central nervous system.²⁷ For a more elaborate description of the pathophysiology of burn-related itch, refer to the above-cited literature.^21-28

One of the most important obstacles to advance the care of burn survivors who are suffering from postburn itch is the lack of routine evaluations in a quantitative manner.^7,39,40 To date, there is no consensus on the gold standard evaluation tool, but there are a number of different options that should be considered and adopted by clinicians. Although the visual analogue scale (VAS) or NRS are commonly used in research, these tools only capture the intensity of itch, leaving changes in episode duration, episodes per day, and the frequency of episodes per week undocumented. These parameters can be particularly important metrics when evaluating postburn itch, thus not surprisingly the episodic nature of itch has been shown to be more sensitive to change than intensity alone.⁴¹ The Questionnaire of Itch Assessment⁴² provides a rich data set that evaluates the multidimensional variables intertwined with the itch experience, such as the emotional, quality of life, and functional impact experienced by patients; however, it takes a long time to administer, thereby potentially creating respondent burden. The 5-dimension (5-D) itch scale,⁴³ Leuven Itch Scale,⁴⁴ and Burns Itch Questionnaire (BIQ)12 have all been shown to be reliable and valid with adult burn survivors. The 5-D itch scale was specifically developed to gather data beyond only intensity data but has the advantages of being applicable to multiple diseases or conditions, brevity, and capability to detect change over time.⁴³ More recent examination of the clinimetric properties of this measure with an adult burn survivor population suggested it should be reduced to 4 dimensions (4-D).⁴⁵ The dimension that was removed in this modified version was distribution, due to the fact that burn survivors localized their itch to their wound and donor sites, therefore scored lower on the distribution dimension compared to other populations.⁴³ The modified 4-D itch scale demonstrated good internal consistency and good association with other measures in the direction and of the magnitude that would be expected and did not exhibit a floor or ceiling effect.⁴⁵ The Leuven Itch Scale⁴⁴ also was developed to be used with populations other than burn survivors who experience itch and includes information about the itch experience, management, and consequences but is less time consuming to administer than the Questionnaire of Itch Assessment.⁴² However, the evaluation of the clinimetric properties was performed on the Dutch version, therefore the English version needs further evaluation. The BIQ12 was specifically developed for the burn survivor population. Confirmatory factor analysis determined that there were 3 subscales: itch severity, sleep interference, and daily life interference, and the analysis showed high internal consistency and ability to distinguish between patients with severe and less severe itch. However, similar to the Leuven Itch Scale, the evaluation of the clinimetric properties was performed on the Dutch version, therefore the English version needs further evaluation. For children, the Itch Man Scale was developed46 and has been shown to be reliable and valid for children 6 years or older⁴⁷; for children under 5 years old, the Toronto Pediatric Itch Scale has been developed and the clinimetric properties evaluated.⁴⁸ 

The complexity of the itch experience and the multifactorial pathophysiology that contributes to it, which may change across time, by default imply that a single treatment intervention is not going to address this challenging problem. This particularly has been shown to be true for those patients with higher itch scores. Fortunately, a number of recent publications provide comprehensive reviews of an array of treatment modalities and several protocols,^{21,22,25-28,49,50} supplying clinicians with a number of nonpharmacological and pharmacological interventions to consider. Hopefully, the increasing awareness and literature surrounding this very important problem will address the fact that as many as 53% of burn survivors experiencing itch were never offered any treatment to alleviate their suffering.¹¹ 

Due to the loss of sebaceous glands in full-thickness and deep partial-thickness burns, the resulting dry skin requires the application of an unscented moisturizer on a regular basis.^9,21,22,25 Topical treatments that cool the site have been proposed,^10,25 although the duration of the benefits has not been well documented and appropriate patient selection must be exercised since cold has been reported by some burn survivors to increase itch.^9,20 Pressure garments have been reported to reduce postburn itch in several studies^51,52; however, the positive benefits noted in the early phase were no longer present at 12 months.⁹ There have been a number of studies that have reported a reduction of itch associated with massage therapy,^37,53-55 but it is difficult to determine how much of the benefit was associated with the application of emollients. The benefits of massage alone in treating mild itch was particularly noted in a randomized, 

placebo-blind, controlled study³⁷ where there were no drop outs in the group with mild itch, suggesting that they were not completely dissatisfied with the benefits they obtained with massage alone as compared with the groups with moderate or severe itch where participants dropped out of the study when receiving massage alone due to dissatisfaction with treatment. The use of gels and gel sheets has been evaluated in a number of studies with respect to their impact on itch; however, the outcomes have been variable.⁵⁶ This may have partially been due to a wide range of itch severity levels at baseline across the studies but also dependent on how itch was evaluated, which varied enormously across studies.

Randomized controlled trials (RCTs) have been conducted for a number of topical preparations that have all been shown to reduce itch in adult burn survivors. These include an antipruritic hydrogel,⁵⁷ beeswax and herbal oil,⁵⁸ colloidal oatmeal,⁵⁹ and Provase⁴¹ (Elta Skin and Wound Care, Carrollton, TX). The Unna boot also was examined in a small RCT of children (n = 6) who had excoriated their graft site.⁶⁰ They were randomly assigned to the Unna boot or conventional dressings, with the parents of the Unna boot group reporting that the children’s appetites, sleep, and play patterns were improved relative to the conventional dressing group.⁶⁰ Unfortunately, this study has not been replicated with a larger group or an adult population.

Positive benefits of a local anesthetic have been reported in a small case series (n = 5) of children⁶¹ with a reduction in mean number of itch episodes and required antihistamine doses, but it does not appear that this has been replicated in a larger population or with adults. Topical doxepin cream also was investigated in a case series of 20 adult burn survivors who were receiving standard care (oral antihistamines, skin moisturizers, and sedatives).⁶² A 7-day trial of doxepin cream applied 3 to 4 times daily following the discontinuation of all standard care except pressure garments resulted in a significant reduction in erythema and itch intensity on the VAS; however, as soon as the cream was discontinued, the itch returned to pretreatment levels.⁶²

The application of transcutaneous electrical nerve stimulation (TENS) was reported initially as an individual case study⁶³ and then as a placebo-controlled, randomized pilot study⁶⁴ involving 20 adult burn survivors who experienced a significant reduction in itch intensity after 3 weeks of treatment. Although both of these reports demonstrated a substantial reduction in itch, there have not been any studies since that have further substantiated the value of this treatment modality.

An evaluation of antihistamines has reported varying levels of patient response where some experienced complete relief (20%), some partial relief (60%), and some no relief (20%), with 37% developing a tolerance, although 85% had a restored response when the dose was increased.⁶ Since then, a number of trials have reported itch reduction with antihistamines.^34,36,65 Thus, due to the fact that about 80% of burn survivors obtained partial or complete relief, antihistamines are commonly prescribed.²⁵ A double-blinded, randomized, crossover trial comparing antihistamine (diphenhydramine) to ondansetron reported that both reduced itch but that ondansetron resulted in greater itch reduction.⁶⁶

Interestingly, a brief report⁶⁷ suggested that patients with antihistamine-resistant itch associated with scars positively responded to a diet excluding potatoes, tomatoes, peppers, and eggplants (foods containing edible solanaceae). Recently, the evidence to support the association of these foods with the itch experience by this subpopulation was expanded in a single-blind, controlled, prospective study.⁶⁸ Participants who had benefited from a solanaceae-free diet and a healthy control group were challenged with systemic exposure to the suspect food and topical exposure to cream containing solanidine or tomatidine. Ninety percent of the scar patients had increased itch associated with both the systemic and topical challenge and 100% to the systemic challenge, but none of the healthy control participants reported any symptoms. Although only 20% of the antihistamine-resistant participants in this study⁶⁸ were burn survivors, the fact that eliminating these foods from their diet, which is both harmless and free, provides an attractive treatment alternative for this subpopulation of burn survivors. Studies confirming these results and determining whether a topical challenge test could identify the subgroup of burn survivors that may benefit from this intervention during the acute phase of care would be extremely valuable.

Another interesting case series reported on 10 burn survivors with severe itch who received botulinum toxin (Botox; Allergan, Coolock, Dublin) injections.⁶⁹ All patients reported that their itch reduced to 0 out of 10 within 4 weeks. There were 40% who reported some reoccurrence, but the intensity was substantially reduced relative to their baseline evaluation.

The literature also contains increasing evidence to support the use of gabapentin or pregabalin. The earliest report of the use of gabapentin for the treatment of postburn itch was a case series in children who had been treated with antihistamines but remained irritable and constantly scratching their wounds.³³ All participants experienced a reduction in itch when treated with gabapentin, although a number of side effects were reported related to behavioral issues. A comparative evaluation in adult and pediatric burn survivors demonstrated that gabapentin alone was more effective than chlorpheniramine alone, and those with higher baseline itch intensity values were more likely to require a combination of pharmacological agents in order to achieve complete itch relief.³⁴ Since then, a case series³⁵ and RCT³⁶ have been published with adult burn survivors, both of which demonstrated significant reductions in itch when treated with gabapentin for the majority of their participants. A more recent study examined pregabalin, a newer structural analog of gabapentin, and reported almost complete resolution of itch in those participants who reported mild (VAS, 2–5/10) or moderate itch (VAS, 6–8/10) and 80% reduction in those with severe itch (VAS, 9-10/10) after 28 days of treatment.³⁷

Within the literature, there have been 4 algorithms or treatment protocols published.^21,22,49,50 The first was based on a risk-adverse approach, where those treatments expected to have the least adverse events are tried first. The authors²² advocate that oral antihistamines and topical emollients be used as the first line of treatment; clinical/health psychologists as the second line; massage, silicone sheeting, hypnosis, TENS, Unna boot, topical nanocrystalline silver, or capsaicin as the third line; and referral to a dermatologist for prescription of topical antihistamines, H1 and H2 antagonists, topical steroids, doxepin, topical anesthesia, or gabapentin or dothiepin cream as the fourth line. 

Alternatively, Richardson et al⁵⁰ argue that the algorithm should be linked to the phases of wound healing, be as simple as possible, and not require a referral to a specialist. They propose 4 stages beginning with stage 1, associated with the inflammatory phase, where they suggest over-the-counter antihistamines and emollients. During stage 2 (where they combine inflammatory and proliferative phases), additional dressing choices (silicone sheeting, nanocrystalline silver, Unna boots) and complementary therapies (TENS, massage) are added. If satisfactory itch control is not obtained, then practitioners would progress to stage 3 (during the proliferative and remodeling phases), where nonover-the-counter antihistamines, other topical treatments (topical anesthesia, capsaicin), anticonvulsants (gabapentin, pregabalin), or naltrexone or antidepressants (doxepin) are added. If itch persists into stage 4 (the remodeling phase), the authors recommend a referral be made to a psychologist for psychoeducation, behavioral assessment, and/or habit reversal be initiated if necessary. 

Bell and Gabriel²¹ included only those treatments where the evidence in the literature was rated as a 5 out of 11 on the PEDro scale (Physiotherapy Evidence Database) and divided their treatment template based on the size of the burn injury, though they do not provide justification for this division. They recommended all burn survivors use moisturizers and receive daily massage. In addition, burn survivors with injuries less than 10% TBSA receive topical colloidal oatmeal treatment daily, topical antihistamines, gel sheeting, and gabapentin; those with injuries greater than 10% TBSA receive oral antihistamines and gabapentin. 

Goutus et al⁴⁹ also used an evidence-based approach but chose to employ the more structured Grading of Recommendations, Assessment, Development, and Evaluation criteria. Their first-line pharmacological agents for both adult and pediatric burn survivors were antihistamines (cetirizine and cimetidine) and gabapentin, and their second-line agents were ondansetron (adults) or loratadine (children). Also, they recommended a number of nonpharmacological adjuncts (moisturizers, cooling, TENS, massage, pressure garments, low-level laser) in addition to the medication in order to maximize symptom relief. Currently, to the best of the authors’ knowledge, there is no evidence to support which of these treatment protocols produces superior results or how long the treatment should be continued to ensure that the itch has completely resolved.

Thus, the treatment options for itch after a burn injury have been the subject of more intense investigation in the recent past, providing clinicians with a number of different treatment options. The algorithms or treatment protocols that have been proposed require further investigation and documentation of their respective outcomes, which would further support evidence-based treatment decisions.

It has now been clearly documented that itch is a pervasive problem following a burn injury that can persist for years; however, it appears to be underevaluated and undertreated. Evidence generated in the past decade has created a paradigm shift, where at one time it was believed that itch was associated with healing wounds and would resolve once wound closure was achieved, whereas today clinicians and researchers recognize that there may be multiple phases (acute and chronic) that may have multiple, concurrent origins (cutaneous, neuropathic, neurogenic, or psychogenic) and hence require several concomitant treatment approaches that will likely need to be modified across time. There are a number of valid and reliable evaluation tools that should be used to document the prevalence and severity of the itch experienced by the burn survivor population, which in turn will serve to objectively document the efficacy of the treatment approaches selected from the currently available toolbox. Further research is required to provide methodologically sound, high-level evidence to support clinicians in their decisions and to clarify which of the treatment protocols efficiently reduces itch in the most cost-effective manner with the fewest number of side effects.

Affiliations: School of Physical and Occupational Therapy, McGill University, Montreal, Quebec, Canada; Centre de recherche du Centre Hospitalier de l’Université de Montréal (CHUM), Montreal, Quebec, Canada; and Villa Medica Rehabilitation Hospital, Montreal, Quebec, Canada

Correspondence: Bernadette Nedelec, BSc OT, PhD, McGill University, Faculty of Medicine, 3654 Promenade Sir William Osler, Montreal, Quebec, Canada H3G 1Y5; bernadette.nedelec@mcgill.ca

Disclosure: The authors disclose no financial or other conflicts of interest.