A skin allergy, or allergic contact dermatitis, produces a red, itchy rash that sometimes comes with small blisters or bumps.
The rash arises when the skin comes in contact with an allergen, a usually harmless substance that the immune system attacks. Allergens trigger allergic reactions. Allergens can come from certain soaps, creams and even pets.
Common allergens include:
- Adhesives, including those used for false eyelashes or toupees
- Antibiotics, such as neomycin rubbed on the surface of the skin
- Balsam of Peru (used in many personal products and cosmetics, as well as in many foods and drinks)
- Fabrics and clothing
- Fragrances in perfumes, cosmetics, soaps, and moisturizers
- Nail polish, hair dyes, and permanent wave solutions
- Nickel or other metals (found in jewelry, watch straps, metal zips, bra hooks, buttons, pocketknives, lipstick holders, and powder compacts)
- Poison ivy, poison oak, poison sumac, and other plants
- Rubber or latex gloves or shoes
You may not have a reaction to a substance when you are first exposed to it. However, you may become more sensitive and develop a reaction if you use it regularly.
Some products cause a reaction only when the skin is also exposed to sunlight (photosensitivity).
- Shaving lotions
- Sulfa ointments
- Some perfumes
- Coal tar products
- Oil from the skin of a lime
A few airborne allergens, such as ragweed or insecticide spray, can also cause contact dermatitis.
Symptoms vary depending on the cause and whether the dermatitis is due to an allergic reaction or an irritant. The same person may also have different symptoms over time.
Allergic reactions may occur suddenly, or develop after months of exposure.
Contact dermatitis often occurs on the hands. Hair products, cosmetics, and perfumes can lead to skin reactions on the face, head, and neck. Jewelry can also cause skin problems in the area under it.
Itching is a common symptom. Itching can be severe in the case of allergic dermatitis. You may have red, streaky, or patchy rash where the substance touched the skin. The allergic reaction is often delayed so that the rash may not appear until 24 - 48 hours after exposure.
The rash may:
- Have red bumps that may form moist, weeping blisters
- Feel warm and tender
- Ooze, drain, or crust
- Become scaly, raw, or thickened
Dermatitis caused by an irritant may also cause burning or pain as well as itching. Irritant dermatitis often shows as dry, red, and rough skin. Cuts (fissures) may form on the hands. Skin may become inflamed with long-term exposure.
Your health care provider will make the diagnosis based on how the skin looks and asking questions about substances you may have come in contact with.
Allergy testing with skin patches may determine what is causing the reaction. Patch testing is used for certain patients who have long-term or repeated contact dermatitis. It requires three office visits and must be done by a health care provider with the skill to interpret the results correctly.
- On the first visit, small patches of possible allergens are applied to the skin. These patches are removed 48 hours later to see if a reaction has occurred.
- A third visit, about 2 days later, is done to look for any delayed reaction.
- If you have already tested a material on a small area of your skin and noticed a reaction, you should bring the material with you.
Other tests may be used to rule out other possible causes, including skin lesion biopsy or culture of the skin lesion.
Your doctor will recommend treatment based on what is causing the problem. In some cases, the best treatment is to do nothing to the area.
Often, treatment includes washing the area with a lot of water to get rid of any traces of the irritant that are still on the skin. You should avoid further exposure to the substance.
Emollients or moisturizers help keep the skin moist, and also help skin repair itself. They protect the skin from becoming inflamed again. They are a key part of preventing and treating contact dermatitis.
Topical corticosteroids are medicines used to treat eczema. They may also be called topical steroids or topical cortisones. Do not use more medicine or use it more often than your doctor advises you to use it.
Your doctor may also prescribe other creams or ointments to use on the skin.
In severe cases, you may need to take corticosteroid pills. Your doctor will start you on a high dose and your dose will be slowly reduced over about 12 days. You may also receive a corticosteroid shot.
Wet dressings and soothing anti-itch or drying lotions may be recommended to reduce other symptoms.
Contact dermatitis clears up without complications in 2 or 3 weeks in most cases. However, it may return if the substance that caused it cannot be found or avoided.
You may need to change your job or job habits if the disorder is caused by exposure at work.