Red, itchy, blisters that appear on the foot are often first diagnosed as athlete’s foot (Tinea pedis). Tinea pedis is a superficial fungal infection that is common in the general population, but it could also be contact dermatitis as they present similarly.
Contact dermatitis is an inflammatory skin condition caused when the skin reacts to and becomes inflamed from exposure to a sensitizing agent. The potency of the sensitizing agent and the immune response of the patient usually determine how long an exposure to the agent is required for a reaction. Poison ivy sap, for example, is such a powerful sensitizing agent that only a microgram can immediately stimulate an intense dermatitis reaction. Less powerful sensitizing agents may take long periods of repeated exposure to stimulate a response.
Shoe dermatitis is very common and is a form of contact dermatitis. Sensitizing agents can include any material from which the shoe we wear is made. Tanning agents, leather and dyes were responsible for most cases early on.
With the advancement in the use of man-made materials, sensitizing agents in shoes may include rubber, thermoplastic, resins, adhesives, dyes, preservatives and metals. Rubber, chromate, formaldehyde resin and colophony are the most common allergens in shoe dermatitis.
Impermeable toe caps made from synthetic materials also hold potentially sensitizing agents against the skin for long periods of time, which may accelerate the onset of a sensitivity reaction as perspiration increases the permeability of the skin.
Shoe dermatitis commonly presents first on the top of the great toe and in the instep where there is typically significant shoe contact. Shoe dermatitis then spreads to other areas, but usually spares between the toes, unlike tinea pedis. Symptoms range from mild itching rash, to itching, swollen blister formation, to even open ulceration with secondary bacterial infection.
An itching rash on the foot that has not responded to topical over-the-counter athlete’s foot preparations may be shoe dermatitis instead. Topical cortisone creams can be tried first, but rarely work for this problem. White cotton socks and prescription-strength corticosteroids are the mainstays of treatment.
See a doctor if you have a skin condition that is not getting better.
David B. Raynor, DPM, is a podiatrist in Inverness and can be reached at 352-726-3668 or at www.AdvancedAnkleAndFootCenters.com.