VitaminMD

Contact dermatitis is skin inflammation that occurs because the skin has been exposed to a substance that irritates it or causes an allergic reaction. A long list of natural and artificial chemicals can trigger contact dermatitis, including ingredients found in soaps, household cleaners, laundry detergents, metal jewelry, perfumes, industrial solvents, cosmetics, fabric finishes, shampoos and even antibiotic ointments. Common skin exposure (or "contact") that can lead to contact dermatitis includes hand washing; housecleaning; wearing a diaper; hiking near poison ivy, oak or sumac; spraying or dabbing on perfume; wearing a metal necklace or bracelet that contains nickel; wearing clothes with metal snaps or zippers; shampooing hair; applying makeup or hair dye; working with industrial solvents; and sitting near a campfire where poison ivy is being burned.

Doctors classify contact dermatitis into two types, depending on the cause of inflammation:
• Irritant contact dermatitis is triggered by exposure to a chemical that is poisonous (toxic) or irritating to human skin. It is not an allergic reaction. In children, the most common form of irritant contact dermatitis is "diaper dermatitis," a skin reaction in the diaper area caused by prolonged contact with the natural chemicals found in urine and stool. Childhood ICD also can develop around the mouth because of skin contact with dribbles of baby food or drools of saliva. In adults, irritant contact dermatitis is often an occupational illness triggered by exposure to strong soaps, solvents or cutting agents. It is especially common among health care workers, homemakers, janitors, mechanics, machinists and hairdressers, but it can occur in anyone whose household chores or hobbies involve exposure to irritating chemicals.

• Allergic contact dermatitis is an immune reaction that occurs only in people who are naturally oversensitive to certain chemicals. With allergic contact dermatitis, the inflammation may not develop until 24 to 36 hours after contact with the substance (allergen). This is because allergic contact dermatitis involves the body's immune defenses, a process that takes some time. Skin allergies vary from person to person. However, among the most common types of allergens responsible are a chemical found in poison ivy, oak and sumac; nickel and cobalt in metal jewelry, clothing snaps, zippers and metal-plated objects; neomycin in antibiotic skin ointments; potassium dichromate, a tanning agent found in leather shoes and clothing; latex in gloves and rubberized clothing; and certain preservatives, such as formaldehyde. About 20% of people in the United States are probably at risk of allergic contact dermatitis because of skin sensitivity to at least one common chemical allergen.

Symptoms of contact dermatitis may vary slightly, depending on the cause:
• Irritant contact dermatitis — In mild cases, there may be only mild redness of the skin. More severe cases may cause skin swelling, blistering or even ulceration. Symptoms usually begin immediately after exposure to the harmful substance, and they are limited to areas of the skin that have been touched, splashed, covered by or immersed in the irritant. For example, a janitor may develop symptoms on his hands after washing the floor with a strong detergent, while a factory worker may develop symptoms on her face after being splashed by an industrial solvent.

• Allergic contact dermatitis — When contact dermatitis is caused by an allergic reaction, it usually causes skin redness, blistering and severe itching. Because allergic contact dermatitis is a form of delayed hypersensitivity, symptoms may not appear for several hours or even days after exposure to the allergen. The location and pattern of the skin reaction may provide clues to the cause of the problem. For example, poison ivy usually appears as a pattern of tiny lines or streaks in places where plant leaves have brushed against the skin. Allergies to metal jewelry often cause rings of skin inflammation around the neck and wrist. An allergy to laundry detergent may cause symptoms that are limited to areas of the body covered by clothing. An allergy to tanning chemicals in leather will affect parts of the feet covered by shoes.

If symptoms of either type of dermatitis are not treated, and the skin continues to be exposed to the substance that is triggering the skin reaction, contact dermatitis may become a long-lasting (chronic) condition. In chronic contact dermatitis, the skin eventually becomes thick, scaly and dry, with color changes and areas of hair loss.

Depending on your pattern of skin symptoms, the doctor will ask about your personal and family allergy history, your history of exposure to irritating chemicals at work or at home, or your contact with poisonous plants. In some cases, your doctor also may need to know the names of specific ingredients found in products that you routinely apply to your skin or hair, especially cosmetics, shampoos, hair dyes, skin lotions, nail polish or antibiotic skin ointments.

After reviewing your history of allergies and chemical exposures, your doctor usually can confirm the diagnosis of contact dermatitis by examining your skin.

In cases of possible allergic contact dermatitis, your doctor may refer you to a skin specialist (dermatologist) for patch testing, in which small amounts of specific allergens are applied to the skin of your back, and then covered with tape. After 48 hours, the doctor removes the tape and examines the skin for signs of an allergic reaction. A second reading is done after three to seven days.

With proper treatment, your symptoms probably will clear up within two to three weeks, as long as you stop exposing your skin to the substance that triggered your skin reaction.

If you continue to have long-term exposure to harmful chemicals or allergens, you eventually may develop symptoms of chronic contact dermatitis that can last for many years.

In general, you can prevent contact dermatitis by avoiding exposure to irritating chemicals, plants, jewelry and other substances that trigger irritant contact dermatitis or allergic contact dermatitis.

To help prevent diaper dermatitis, change baby diapers frequently, clean the soiled area with warm water and a soft cloth, and apply a protective coat of zinc oxide ointment. Avoid using store-bought wipes and cleansers on your child's skin, because these products can trigger skin reactions.

To help prevent work-related incidents, the U.S. National Institute of Occupational Safety and Health (NIOSH) has established the Allergic and Irritant Dermatitis Team to research contact dermatitis in the workplace. The team's goal is to give workers reliable information about protective equipment, protective clothing and skin creams that can be used to reduce contact dermatitis on the job.

Your doctor usually will treat contact dermatitis with the following:
• An oral (by mouth) antihistamine to control the itch — Common antihistamines include diphenhydramine (Benadryl), hydroxyzine (Atarax), cetirizine (Zyrtec), loratadine (Claritin) and fexofenadine (Allegra). Of these, the last three are less likely to cause drowsiness.

• A corticosteroid to relieve skin inflammation — In most cases, the corticosteroid can be applied as a cream or ointment containing one of the following: hydrocortisone (Hytone), hydrocortisone valerate (Westcort), desonide (Tridesilon or DesOwen), hydrocortisone butyrate (Locoid), desoximetasone (Topicort), fluocinonide (Lidex) or amcinonide (Cyclocort). If symptoms are severe, corticosteroids can be given by mouth or by injection.

• A moisturizer to help restore the normal texture of the skin — Your doctor probably will suggest a nonirritating ointment or cream that contains few potential allergens. Examples include petroleum jelly, Vanicream, Cetaphil and Eucerin. For many people, oatmeal baths (Aveeno) also help.

Call your doctor whenever you are troubled by an area of skin that is red and very itchy, or skin that is cracked, blistered or painfully dry. Even if you are certain that your skin problem is "just a case of poison ivy," your doctor may be able recommend a prescription medication that will relieve your symptoms better than over-the-counter remedies.

For most cases of contact dermatitis, the outlook is excellent, as long as you can identify the substance that triggered your contact dermatitis and avoid it in the future.