Allergies

Allergy-causing substances (called allergens) touch the skin and can cause a reaction including itching, redness, scaling, a rash, and blisters.

What does an allergic contact rash look like?

In severe cases the skin gets red, itchy, and swollen, and develops tiny blisters. These blisters often break and leave crust and scales. The skin becomes thick, red, and scaly with long-term exposure to an allergen. Later the skin may darken and become leathery and cracked.

eczema

How is it diagnosed?

Allergic contact dermatitis can be hard to tell apart from non-allergic rashes, such as irritant contact dermatitis. Identifying materials that your skin encounters will help your dermatologist pinpoint the allergen, as will inspecting the rash.
Allergy skin test called patch tests are generally a safe, easy way to detect contact allergies.

What is the treatment?

Mild rashes can typically be treated with steroid creams and/or oral antihistamines. You also may need to apply moist compresses to blisters for a few days and cover blisters with bandages. For severe rashes, your dermatologist may give you oral corticosteroids or injections. You may need other anti-inflammatory medicines. If your skin becomes infected, you may get antibiotics.