Allergic Contact Dermatitis

Allergic contact dermatitis is inflamed skin that occurs when allergy causing substances (allergens) touch the skin. When someone is sensitive to an allergen that comes in contact with their skin, is causes itching, redness, scaling, rash, and if severe, blistering can result. The best way to prevent this type of rash is to find out what you’re allergic to and avoid contact with it.

In early (acute) severe cases, such as poison ivy, 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 my darken and become leathery and cracked.

Common allergens include metals, rubber, dies, antibiotics, cosmetics, preservatives, and fragrances. Poison ivy, poison oak, and other plants can also cause this rash.

Metals

• Metals are in many products, including jewelry, metal buttons, clothing fasteners, dental fillings, and cell phones. Contact allergy also can occur from medical implants, such a stent in the arteries of the heart or implants for hip and knee replacements.
• Nickel is the most common metal to cause skin allergies. Nickel is in many products, including gold platted jewelry. For instance, earrings containing nickel often cause a rash on the ear lobe. People who are allergic to nickel should wear nickel free jewelry.

Rubber

• Natural latex and synthetic rubber products often cause allergic contact rashes. Chemical additives in rubber are most often the cause of the allergy. Despite being a well known allergen, synthetic rubber product called polychloroprene is still in wide use.
• Latex rubber gloves are a frequent source of allergic contact rash on the hands. People are more likely to get this type of allergy if they have inherited allergies, food allergies, or hand dermatitis (eczema). People with a latex allergy should wear vinyl or nitrile gloves. They should wear shoes with soles that are not rubber and underwear with elastic bands that do not contain latex.

Hair Dyes

• Some people are sensitive to hair dyes and other products containing paraphenylenediamine (PPD). This chemical is in a “permanent” (long lasting) hair dyes that are mixed with other chemicals, such as peroxide, before use. While PPD is the most common allergen linked to hair dyes, other compounds can cause allergies.
• People allergic to PPD should not use permanent hair dyes. Follow the package instructions, or ask your hairdresser to test whether you are sensitive, before using any hair dye. People who are allergic to PPD can use temporary hair dyes or color rinses. Some people, though, may react to these dyes as well.
• PPD may also be mixed with Henna for temporary tattoos. People who are allergic to PPD will react to these tattoos. In bad reactions, scars may result.

Topical Antibiotics

• Topical antibiotics are frequently used in wound treatment. Some topical antibiotics have caused allergic contact rashes. These include neomycin, bacitracin, gentamicin, and polymyxin. The antibiotic that most often causes an allergic contact rash is neomycin. Neomycin is in both prescription and non-prescription antibiotic creams, ointment, lotions, eardrops, and eyedrops. Some topical medicines mix neomycin with corticosteroids and other antibiotics, such as triple antibiotic first aid creams, and should be avoided.

Skincare Products

• Perfumes, lotions and cosmetics are common causes of allergic contact rashes. Some people are sensitive to the fragrance chemicals. People with fragrance allergy can use fragrance free products. “Unscented” products, though, may still have a masking fragrance to cover up the smell of the chemicals. Additionally people can be sensitive to one or more preservatives that prevent skin care and personal care products from spoiling.

Poison Ivy and Related Plants

• Poison ivy, poison oak and poison sumac cause allergic contact rashes for millions of people each year. About 85% of people react to the oil sap in these plants, but most often not until the second time they touch them. An itchy, blistering rash results about 1 to 3 days after contact. Often there are lines of small blisters with the plant brush against the skin. People who are sensitive to poison ivy, oak and sumac can also be allergic to other plant oils and botanical extracts. These can cause an allergic contact rash:
o Tea tree, sesame, cinnamon, peppermint, olive and castor oils
o Furniture lacquer (varnish) obtained from the Japanese lacquer tree.
o Mango rinds
o Cashew shells

Allergic contact dermatitis is often diagnoses clinically based on the appearance/location of the rash and a good history. Allergic contact dermatitis can be hard to tell apart from non-allergic rashes, such as irritant contact dermatitis. Your dermatologist will ask you to list materials that your skin encounters at work and elsewhere. This thorough health history will help your dermatologist pinpoint the allergen, as they inspect the rash.
Often, you will also need allergy skin test called patch test. Patch tests are a safe, easy way to detect contact allergies. Patched differs from intradermal (injection), prick, or scratch test, which put the allergen into the skin. And patch test, the dermatologist or allergist put small amounts of your suspected allergens on strips of tape and applies the strips to the skin. After two days, the doctor removes the strips. A red spot at the site of the patch shows an allergy.

Mild rashes most often respond to steroid creams and or oral antihistamines. You may also need to apply moist compresses to blisters for a few days and cover blisters with bandages. For more serious rashes, your dermatologist may give you oral corticosteroids. If your skin becomes infected, you may need antibiotics.