An allergic contact rash (also called allergic contact dermatitis) is a skin reaction that occurs when allergy-causing substances (allergens) touch your skin. If you are sensitive to them, the allergens can cause an itchy rash on swollen, reddened skin. The skin may blister, ooze, form a crust, or flake off. Sometimes the rash may take 2-3 days to develop after exposure to the allergen.

The best way to prevent this type of rash is to find what you are allergic to and avoid contact with it.

COMMON CAUSES

Metals

You come in contact with products containing metal every day, such as your jewelry, coins, zippers and the buttons on your jeans. Metals can also be found in dental fillings, keys, food and cell phones. You may even come into contact with metal on the job. Allergic contact rashes are common in industries that use cement, metal, leather, some matches, paints, epoxy-based sealants, and anti-rust products. Allergic contact rashes can also occur from medical implants, such as stents 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 metal products, including gold jewelry.

• Earrings containing nickel can cause a rash on the ears. People who are allergic to nickel should wear nickel-free jewelry and look for earrings with nickel-free posts and backings. Platinum, sterling silver, and pure gold (18K or greater) are less likely to cause an allergic reaction.
• Certain metals are used to tan leather for shoes and can cause “shoe dermatitis” (a rash on the foot). Vegetable-tanned footwear is an option.

Allergic contact dermatitis to nickel sulfate

Rubber

Latex and synthetic rubber products can cause allergic contact rashes. Latex rubber gloves can cause an allergic contact rash on the hands. You are more likely to have this type of allergy if you have inherited allergies, such as eczema or asthma, food allergies, or hand dermatitis.

• If you have a latex allergy, you should wear vinyl gloves, shoes with soles that are not rubber, and underwear with elastic bands that do not contain latex.

PPD in Hair Color

Some people are sensitive to hair color and other products containing para-phenylenediamine (PPD). This chemical is in long-lasting hair colors that are mixed with another chemical, such as peroxide, before use.

If you are allergic to PPD, you should not use permanent hair color. Try temporary hair color or color rinses. If you are coloring your hair at home, you should always test whether you are sensitive to hair color or color rinses before using. Do a skin patch test, typically recommended on most boxed hair color. Put a bit of dye on your skin and wait 48 hours to see if a reaction develops. If you do not see a reaction, it’s likely you can safely color your hair at home or the salon.

PPD may be mixed with henna for temporary tattoos. If you are allergic to PPD, you will likely react to these tattoos. In severe reactions, blistering and scarring may result.

PPD in Clothing

Allergies to PPD also may cause sensitivity to inks and dyes used in other products, such as clothing.

If you are allergic to PPD, you may find wearing dark-colored clothing difficult. Many of the dyes that make dark colors come from PPD.

Avoid clothing made of synthetic fibers like polyester, acrylic, or nylon. Many of the dyes used to color these materials come from PPD.

Topical Antibiotics

Many topical antibiotics can cause allergic contact rashes. These are typically over-the-counter medications or treatments that you apply to the skin after you cut or scrape it. These include neomycin, bacitracin, gentamicin, kanamycin, and polymyxin.

The most common ingredients in topical antibiotics to cause allergic contact rashes are neomycin and bacitracin. These can be found in both prescription and non-prescription products, including non-prescription antibiotic creams, ointments, lotions, ear drops and eye drops.

• If you are allergic, you should avoid these ingredients in topical antibiotic products. It is also regularly found in other antibiotics and corticosteroids, such as in over-the-counter triple antibiotic ointment.
• For simple skin wounds or scrapes, use plain petroleum jelly on them.

Skin Care Products

Perfumes, lotions and cosmetics are common causes of allergic contact rashes. You may be sensitive to the fragrance chemicals or preservatives that prevent skin care products from spoiling.

• Look for fragrance-free products. Be careful though because even products labeled “unscented” may still have a “masking” fragrance to cover up the smell of the chemicals.

Poison ivy rash

Poison Ivy and Related Plants

Poison ivy, poison oak, and poison sumac cause allergic contact rashes for millions of North Americans each year. The oily sap in these plants can cause an itchy, blistering rash between one and three days after contact. About 85 percent of people react to oily sap in these plants but most often not until the second time they touch them. Often there are lines of small blisters where the plant brushed against the skin.

• If you are sensitive to poison ivy, oak, and sumac, you may also be allergic to other plant oils and botanical extracts, such as tea tree, sesame, cinnamon, peppermint, olive, and castor oils.
• You also may be allergic to furniture lacquer (varnish obtained from the Japanese lacquer tree), mango rinds, and cashew shells.

HOW ARE THEY DIAGNOSED?

Allergic contact rashes can be hard to tell apart from non-allergic rashes. Your dermatologist will inspect your rash and ask you to list the products that you encounter during the day at home or work. These clues will help your dermatologist identify the potential allergen. It is also helpful to keep a diary of things that are touched and when a reaction occurs.

Your dermatologist can use these clues to help narrow down the source of your sensitivity.

You may need an allergy skin test called patch testing. Patch testing is a safe, easy way to diagnose contact allergies. It requires three visits. On the first day, a small amount of your suspected allergens is placed on strips of tape and applied to the skin. After two days the strips are removed. There may or may not be a reaction. If there is a red spot at the site of a patch on the third visit (generally four days after the patches were initially placed), you may have a contact allergy.

HOW ARE THEY TREATED?

Mild rashes most often respond to steroid creams and/or oral (taken by mouth) antihistamines. You also may need to apply moist compresses (cloths) to blisters for a few days and cover blisters with bandages. The wet wraps help keep skin moist, improve the effectiveness of topical medicine, and can have a cooling anti-itch effect on the rash.

Allergy to Fragrance in Lip Balm

For very bad rashes, your dermatologist may give you oral corticosteroids or injections (shots). You may need other anti-inflammatory medicines or immunologic therapies. If your skin becomes infected, you may need antibiotics.

Once you know the allergen that causes the reaction on your skin, you should avoid it. Your dermatologist will help you determine what you need to avoid and can suggest products that do not contain the allergen.

A board-certified dermatologist is a medical doctor who specializes in treating the medical, surgical and cosmetic conditions of the skin, hair and nails. To learn more or to find a board-certified dermatologist in your area, visit aad.org or call toll free (888) 462-DERM (3376).

All content solely developed by the American Academy of Dermatology.

Copyright © by the American Academy of Dermatology and the American Academy of Dermatology Association.

Images used with permission of the American Academy of Dermatology National Library of Dermatologic Teaching Slides

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