An id reaction is an itchy rash with blisters, or vesicles. It usually occurs on the sides of the fingers, but it can also be found on the chest or arms. This rash occurs in response to a fungal infection somewhere else on the body, especially athlete's foot.
The id reaction is thought to be an allergic response to fungi. Treating the fungal infection makes the id reaction rash go away.
The fungal infection causing this itchy response can be very mild. Sometimes an id reaction is the only way a person knows they have athlete's foot.
Sources:
Fritsch, Peter, and Norbert Reider. "Other Eczematous Eruptions." Dermatology. Ed. Jean Bolognia. New York: Mosby, 2003: 121-2.
Habif, Thomas. "Eczema and Hand Dermatitis." Clinical Dermatology, 4th Edition. Ed. Thomas Habif, MD. New York: Mosby, 2004. 63.
