When A Patient Presents With Symmetrical Lesions On The Toes

A 32-year-old Caucasian female presents to the office with swollen, sore, irritated, itchy toes of both feet and a symmetrical distribution on the tops of the toes.
She notes that the redness started four weeks ago. It was on the third toe initially but is now on other toes as well, according to the patient. There is no scaling or maceration in the interspaces, and no scaling on the rest of the foot.

The patient has a history of vaginal infections and had been taking fluconazole (Diflucan, Pfizer) approximately one month prior to her presentation. She has also been taking amitriptyline (Elavil, AstraZeneca) for pubic-related pain. She has sensitive skin as well as a history of hay fever. She denied being labeled as atopic, which refers to diseases that are hereditary and often occur together (asthma and atopic dermatitis).
The patient has no history of eczema or psoriasis. She has been using over-the-counter antifungals on the toes as recommended by her internist with no resolution of the rash. The patient presented in stylish leather shoes with the leather over the toes only. She says she rarely wears socks and only wears sneakers on the weekend.

What You Should Know About Contact Dermatitis
Using patch testing, I diagnosed the patient with allergic contact dermatitis to butylphenol formaldehyde resin in the leather upper portion of her shoes. I prescribed topical corticosteroids for two weeks and the dermatitis on her toes improved significantly after she stopped wearing her leather shoes completely for one month. She wore canvas shoes and wood clogs during that time period.
Contact dermatitis is an acute inflammatory reaction caused by a substance in contact with the skin. There are irritant and allergic types. Irritant dermatitis occurs when a substance causes direct damage to the skin. Allergic contact dermatitis occurs when a substance that serves as an allergen elicits a type IV cell-mediated hypersensitivity reaction.1
Shoe contact dermatitis occurs in a small percentage of the population and is caused by an allergic reaction to a substance in the shoe. The most common causes are dyes, leather, shoe rubber, adhesives, trim and biocides (the pesticides used on the rawhides to kill organisms). Bear in mind that topical medications, steroids, antifungals, antibiotics (neosporin), bag balm, botanicals and socks may cause allergic reactions that may masquerade as shoe contact dermatitis.2 It is important to look at both feet to see if the rash is symmetrical.
The most common shoe allergens are rubber, chromate and butylphenol formaldehyde resin (see “A Guide To Common Shoe Allergens” above).
Along with the fact that patients often wear footwear without socks during all months of the year, the moisture and humidity in shoes increases skin contact with allergens.
Most patients with shoe dermatitis have hyperhidrosis and many are atopic. One should consider shoe dermatitis in both children and adults with foot eczema.
The pattern of shoe dermatitis usually corresponds to the location of the offending substance in the shoe. Dorsal foot shoe dermatitis has been attributed to allergens in glues as well as chromates and vegetable tannins in leather. Plantar shoe dermatitis may be due to rubber or other materials.
Sole involvement tends to spare the instep and toes’ flexural creases. Shoe dermatitis is usually symmetrical but may also be patchy or unilateral. Classically, allergic contact dermatitis to shoes manifests as a rash on the dorsum of the feet or toes. However, a subset may only have involvement on the soles of the feet. One author explains that the culprit was the neoprene glues contained in the orthotics that patients wore.5 Patients will routinely wear orthotics in their shoes without socks. In the end, one has to be a detective to determine the cause of the rash or dermatoses.

What You Should Consider In The Differential Diagnosis

Nummular eczema. These lesions are usually round and coin-shaped. They are not generalized lesions. The patient has no history of exposure to an allergen.
Atopic eczema. Patients have a chronic rash with flexural distribution.
Dermatitis herpetiformis. The rash is localized to elbows and knees.
Scabies. One may see this in other family members. It is localized to the dorsum of feet and ankles, and spreads to other areas. Skin scraping is positive.
Tinea pedis (inflammatory). This includes itching and maceration between toes, which was not present in the patient. Pitted keratolysis. This bacterial disease is due to hyperhidrosis of the stratum corneum. There is little inflammation and distinct pits are noted.
Pustular psoriasis. This is usually not symmetrical and on a larger area.
Lichen planus. Patients have purple flat, topped bumps that are itchy. This was not present in the patient.
Atopic dermatitis. One usually sees this condition among younger patients and on plantar skin as well. In the absence of an allergen in this case, atopic dermatitis would be a possible diagnosis.
Raynaud’s disease. A spasm of blood vessels causes a change in color. The three-phase color sequence is white to blue to red.
Mechanical irritant dermatitis. This results from abnormal foot mechanics.
Exanthematous drug eruption. The rash could be due to the fluconazole but these rashes normally start on the trunk and are not usually symmetrical.

A Guide To Clinical Manifestations And Diagnostic Testing
The patient may have a rash ranging from a mild itch to severe itching. One may also see inflammation, swelling, redness, blisters (crusts and scales, which are old blisters), fissuring, burning, pain or swelling. In severe cases, open sores can result in bacterial skin infections.
With long-term exposure to an allergen, the skin can become lichenified. Usually, the involved areas are on the tops of the foot and toes. However, contact dermatitis can also affect the sole of the foot, the legs and the sides of the feet and heels. The area in between the toes is not usually affected.
One should perform patch testing to discover and/or confirm a contact allergy. Patch testing does not diagnose contact dermatitis. People with a contact allergy develop dermatitis to substances.
Many companies provide the patch test kits that have the allergens in them already. The Thin-Layer Rapid Use Epicutaneous Test®, also known as the T.R.U.E. Test (Allerderm), is a convenient, ready-to-use patch. It is recommended that one seek out a physician who has had experience in administering and reading the test. If commercial patches and tape are not available, one may improvise by using Band Aids as patches with occlusive tape over the Band Aid. The allergen must be 1.0 cm2 of surface area and it goes under the Band Aid.4

Inside Insights On Treatment
One can treat acute contact dermatitis with wet dressings of Burrow’s solution or diluted vinegar; short courses of systemic steroids; short or prolonged treatment with topical steroids; and/or coal tar and emollients. Patients also must wear shoes that are free of the causative allergens.
If the patient cannot find an allergen-free shoe to wear and wants to try wearing regular shoes, Storrs suggests the following preventative measures.
• Decrease the risk of hyperhidrosis with tea soaks or Drysol.
• Buy all new socks as socks absorb allergens.
• Use insoles of cork or piano felt over the plantar foot bed if necessary.
• Try corticosteroid spray (Kenalog) before the use of “potential problematic shoes.” Keep in mind that this is not a long-term solution.
• Wear shoes made of wood or plastic, all sewn shoes made of leather or Birkenstock sandals.2

Dr. Morse is the President of the American Society of Podiatric Dermatology. He is a Fellow of the American College of Foot and Ankle Surgery, and the American College of Foot Ankle Orthopedics and Medicine. Dr. Morse is board certified in foot surgery.

References:

1. Barone EJ, Jones JC, Schaffer JE. Skin Disorders. Lippincott Williams and Wilkens. Philadephia. 2000
2. Storrs FJ. Foot Dermatitis at https://www.acderm.com/FOOTDERMATITIS.pdf
3. Adams AK, Warshaw EM. Allergic contact dermatitis from mercapto compounds. Dermatitis 2006;17(2):56-70.
4. Pariser DM, Caserio RJ, Eaglstein WH. Techniques for Diagnosing Skin and Hair Disease. Second Edition. Thieme Inc. 1986
5. Blair K. Latex Substitute As an Allergen. Dermatology Times of Canada. January 2004.