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Chemical Allergies

They promise to make your skin soft, your hair shiny, and your laundry springtime fresh, but for some people the chemicals in shampoos, cosmetics, and detergents trigger allergic skin reactions.

Causes of Chemical Allergies

Allergic skin reactions, called allergic contact dermatitis, can occur when your immune system overreacts to chemicals that are normally harmless. Often these are chemicals in products that you are exposed to or use repeatedly, such as cleaners, colognes, hair dyes, and personal hygiene items. Even if you have no initial reaction to these products, regular use can eventually cause sensitivity and reaction to them. Some products cause a reaction only when they contact the skin and are exposed to sunlight.

Anything your body is allergic to is called an allergen. Although cosmetics and personal hygiene products contain a variety of potential allergens, some of the more common ones are:

Fragrances in soaps, colognes, deodorants, body creams, cosmetics, detergents, and tissues.
Preservatives and antibacterials, added to many liquid products to keep them from becoming rancid or contaminated.
Formulation excipients, or inactive substances added to thicken, color, or lubricate a product.
Cocamidopropyl betaine, paraphenylenediamine, and glycerol thioglycolate, three chemicals common in permanent hair dyes and other hair products.
Formaldehyde resin, an ingredient in many nail care products.
Sunblocks or sunscreens, frequently present in cosmetic moisturizers, lip balms, hair preparations, and foundations.

Symptoms of Chemical Allergies

Your skin is one of the first places where allergy symptoms can appear. When your skin comes into contact with products containing chemical allergens, symptoms often occur 24 to 48 hours later, but can start as late as a week after exposure. Although each person may experience different symptoms of these allergies, some of the most common symptoms are:

Skin redness
Scaly patches of skin
Blisters that ooze
Skin burning or itching, which may be intense
Swelling of the eyes, face, and genital area
Hives
Sun sensitivity
Darkened, "leathery," and cracked skin

The most severe reaction is at the contact site; however, if you get the allergen on your finger and then touch another part of your body, such as your face or neck, you can set off an allergic reaction there.

Because the symptoms of allergic contact dermatitis can resemble other conditions, you should see a doctor if you experience the symptoms listed.

Diagnosing Chemical Allergies

If your doctor suspects a chemical allergy, a skin patch test may be useful for identifying the most likely substances that are causing you to have an allergic response. This test involves placing small samples of chemicals on an area of your back. Your doctor will check the area 48 hours later and again at about 96 hours later to see if a rash develops.

Keeping a log of information related to your skin condition will help your doctor in making the diagnosis. Your log should include details such as the following: