Allergic Contact Rashes

Mrs. Smith's lips began to itch and blister. After testing, her dermatologist said she was allergic to nickel. The problem? Holding nickel-plated hairpins in her mouth when setting her hair. When she stopped, so did the itching.

Tom Black's big toe was red and sore. His dermatologist diagnosed an allergy to rubber. The lining in one of Tom's shoes had worn away, so his toe rubbed against a rubber lining. When he stopped wearing the shoes, his toe got better.

These are examples of allergic contact dermatitis. This condition can be caused by almost anything that comes into contact with the skin. A substance that causes allergic contact dermatitis is called an "allergen." Most people do not react to an allergen. Some people will become allergic to a substance with time. Further exposure will produce an itchy rash.

Allergic contact dermatitis is not usually caused by things like acid, alkali, solvent, strong soap or detergent. These harsh chemicals, which can produce a reaction on anyone's skin, are known as "Irritants." Although some chemicals are both irritants and allergens, allergic contact dermatitis results from brief contact with substances that don't usually cause a reaction in most people.

What Dermatitis Looks Like

The skin gets red. swells, and blisters appear. Blisters may form and break, leaving crusts and scales. Later the skin may darken and become leathery and cracked. Allergic contact dermatitis can be difficult to tell from other rashes.

Allergic contact rash

Discovering the Cause

The dermatologist and patient will discuss the materials that touch the person's skin at work and home, to identify the allergen. The dermatologist may also perform patch tests. Patch tests are a safe and easy way to diagnose contact allergies. Small amounts of the possible allergens are applied to the skin for a fixed time, usually two days. Common allergens include nickel, rubber, dyes, preservatives, fragrances, and poison ivy, poison oak, and related plants.

Nickel Dermatitis

Nickel, part of certain metals', is found in many products. Many chrome-plated objects contain enough nickel to produce a reaction in sensitive people.

Stainless steel also contains nickel. But it is bound so tightly that it is safe for most nickel-sensitive individuals.

Earrings containing nickel can cause earlobe dermatitis, a very common problem in people allergic to nickel. This may start with the needles used to pierce ears and earrings.

Only sterile stainless needles should be used for piercing. After piercing wear only nickel- free earrings for at least the first three weeks.

Clothing fasteners made of nickel-buckles, zippers, buttons and metal clips-can cause dermatitis. Nickel-sensitive people can substitute nylon accessories.

Sweating increases dermatitis in nickel sensitive people. In the summer, items containing nickel can cause an itchy, prickly sensation within 15 to 20 minutes of touching sweaty skin. A rash may appear within a day or two. These same items can be worn for several hours without any problems, if sweat is not present.

Rubber-A Frequent Offender

Rubber products often cause allergic contact dermatitis. Chemicals in rubber cause the reaction. Rubber-sensitive people must use something else.

Rubber can also cause immediate allergic reactions, including itching or burning and hives (welts) under the rubber object. Some people experience itching and tearing eyes and, rarely, shortness of breath. This is more common in people who wear tight fitting rubber gloves, such as medical workers. Rubber gloves may also cause dermatitis on the skin of the hands under the glove. Vinyl or other synthetic gloves may be substituted.

Many women with rubber allergy can wear under garments with an elastic called spandex if they do not have rubber-backed fasteners or edges. Girdles and bras with no rubber are available.

Most cases of allergic contact dermatitis from shoes are caused by ingredients in the rubber used in the shoe's construction. Adhesives, both rubber and non-rubber, can also cause problems. Even leather shoes may contain adhesives. Shoes without rubber should be substituted.

Hair Dyes

Most people can color their hair without difficulty. However, some are sensitive to paraphenylene-diamine (PPD). This ingredient is found in permanent hair dyes that are mixed with other chemical, such as peroxide, before application.

People allergic to PPD should not use any permanent hair dyes. About one fourth of the people allergic to PPD are also allergic to ingredients in semipermanent dyes. Follow the package instructions for a patch test before using any hair dye.

Most PPD allergic people can use temporary dyes or rinses, to blend in gray and brighten hair. A few people, however, will react to these dyes too.

While PPD dyes are rare in clothing, other dyes that may cross-react with PPD are. As a result, some PPD-sensitive patients cannot wear dark clothing, but can wear lighter shades.

About 25% of PPD sensitive people are also allergic to certain local anesthetics, like benzocaine, that are chemical relatives of PPD. Substitutes may be used.

Skin Care Products

Perfumes, lotions, and cosmetics may cause allergic contact dermatitis. Some people are sensitive to the fragrance chemicals used in skin care products. Others are sensitive to the preservative chemicals needed to prevent skin care products from spoiling.

Fragrance-free products can be used by people with a fragrance allergy, but unscented products still have a fragrance added to cover up the smell of the chemicals. There are very few truly preservative-free products, but persons may be sensitive to only one preservative chemical and not others.

Chromates

Chromates contain chromium, and are commonly responsible for allergic contact dermatitis from cement, leather, some matches, paints and anti-rust products. Contact to chromium is common in Jobs in the automobile, welding, foundry, cement, road and building repair industries. Chromates are used to tan leather for shoes and clothing. "Shoe dermatitis" may result from leather containing chromates. Vegetable-tanned footwear can be used.

Some matches contain chromates. Touching unlit matches can contaminate fingers. Fumes from a lit match and the charred match head also contain traces of chromates. Placing used matches in a pocket will contaminate the pocket lining, as will book matches.

Poison Ivy and Its Relatives

This plant family includes poison ivy, poison oak, and poison sumac. In the U.S. these plants produce many cases of allergic contact dermatitis. The reaction looks the same from all of them. Often patients develop lines of small blisters on the skin where the plant brushed against them.

People sensitive to poison ivy, oak, and sumac are often allergic to oils from plants from other countries. A furniture lacquer obtained from the Japanese lacquer tree contains such an oil, as do mango rinds and cashew shells.

Conclusion

People with allergic contact dermatitis should:

• Avoid the allergen that causes the reaction, and chemicals that cross-react with it. Your dermatologist can help you identify items to avoid.
• Use products that do not cause reactions.

Revised 1997
© 1994 American Academy of Dermatology
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