What is an Id Reaction?

What You Need to Know About an Interface Dermatitis Reaction

Contact Dermatitis. Credit: BSIP / Contributor / Getty Images

An interface dermatitis (ID) reaction, also known as autoeczematization, 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. 

What does an id reaction look like?

Id reactions can present itself in a variety of different ways:

  • localized or widespread vesicular lesions,
  • maculopapular or scarlatiniform eruptions,
  • erythema nodosum,
  • erythema multiforme,
  • erythema annulare centrifugum,
  • Sweet's syndrome,
  • guttate psoriasis,
  • and autoimmune bullous disease.

​However, in general, they are typically itchy. Id reactions can also be small, fluid-filled spots; solid bumps; red, raised patches; deep, raised, bruise-like areas on the shins; pinkish red spots that resemble targets; or hives.

What causes an Id Reaction?

The most common cause of id reactions is a fungal infection somewhere else on the body, especially athlete's foot. But it may also occur because of bacterial, viral, or parasitic infections. Id reactions can also occur to therapies. 

ID is also typically seen in autoimmune skin disorders such as lichen planus, cutaneous lupus erythematosus, and may also appear during immune reactions against drugs, viruses, and tumors. For instance, one study found that id reactions occurred to bladder cancer patients undergoing BCG therapy.

How is an id reaction treated?

In fact, how the id reaction presents itself depends on what caused it in the first place. Your dermatologist will identify it so that the underlying infection can be treated. They do this by taking scrapings of the area affected.

Basically, the id reaction is thought to be an allergic response to fungi — or bacteria, or virus, or parasite— and treating the fungal infection makes the id reaction rash go away.

 Sometimes an id reaction is the only way a person knows they have an infection. To relieve symptoms, your doctor may prescribe corticosteroid creams, or oral anti-itch drugs.

Common Infections that Cause Interface Dermatitis

An ID reaction may occur for numerous reasons. Here are some of the more common infections that trigger it:

  • Ringworm— also known as tinea corporis and tinea capitis, is actually not caused by a worm, but by fungi.
  • Athlete's foot — there are three types to be familiar
  • Jock Itch — also known as tinea cruris, is a fungal infection of the skin in the groin.
  • Spider Bites — sometimes it is difficult to tell the difference
  • Tinea Versicolor — also known as pityriasis versicolor, is a superficial fungal infection of the skin that is often confused with other common rashes.
  • Intertrigo — a yeast infection of skin folds caused by Candida albicans.


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