By Gary M. White, MD
The term shoe dermatitis applies to allergic contact dermatitis of the foot in response to one or more components of the shoe.
- The most common culprits in one study were rubber chemicals (40.4%), adhesives (32.5%) and leather components (20.1%).
- The most common allergens are p-tert-butylphenol-formaldehyde resin (PTBFR- an adhesive), potassium dichromate (used in leather tanning), and rubber allergens (mercaptobenzothiazole (MBT), tetramethylthiuram, carba and black rubber mix).
- Chromium salts (chromium sulphate) used in the tanning process can cause chromium sensitivity in a small number of individuals. A common use of chrome-tanned leather is in footwear uppers and linings.
- Dye allergy: Consumers with these allergies should avoid footwear with dyed textile and leather linings, instead selecting footwear with white textile or undyed leather linings and in-sock.
- Formaldehyde allergy: The footwear materials most likely to contain formaldehyde are textiles (where it may be used as a stiffener) and leathers, where it may be present in some synthetic tannages or finishes.
- Nickel allergy: Occasionally, metal rings, clasps etc in footwear can cause a rash in nickel-sensitive individuals.
The condition may be unilateral if one foot sweats more than the other. The tops of the toes, lateral sides of the foot and sole with sparing of the instep is typical.
Patch testing should be done and the offending allergen(s) avoided. Not only the offending shoes but also socks worn with those shoes must be replaced to eliminate exposure to the antigen. Occasionally, the socks themselves may be culprit if they have specific dyes, rubber (for non-sticky soles) or elastic. A variety of websites and companies give advice and sell hypoallergenic footwear. The footwear must of course be tailored to the specific offending allergens of the patient.
For those with allergy to mercaptobenzothiazole (MBT), consider the following:
- Wear solid leather shoes like moccasins or wood clogs (no inner or outer rubber soles).
- Socks and stockings worn with shoes containing MBT can be contaminated and may not wash out easily and should be discarded.
- Leather shoes can have MBT in soles, lining and adhesives.
- Ask your shoe store for rubber free shoes.
Blistering shoe dermatitis.
ACD to the straph of a thong.
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