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Contact dermatitis happens when the skin becomes irritated or inflamed after coming in contact with a substance that triggers an allergic reaction. It bears some of the same symptoms as the six other types of eczema. But unlike atopic dermatitis — the most common and difficult-to-treat form of eczema — it doesn’t run in families and isn’t linked to other allergic conditions such as hay fever or asthma.
According to Dr. Jeff Yu, a dermatologist specializing in allergic contact dermatitis and occupational dermatitis in adults and children at Massachusetts General Hospital in Boston, contact dermatitis can occur when the skin is exposed to anything from chemicals in cosmetics and household products to nickel or plant oils. It really depends on the patient and what they’re allergic to, he explained.
In addition to itch, contact dermatitis may cause burning or blistering of the skin, and can have a major impact on a person’s quality of life, Yu said.
“Contact dermatitis can lead to significant sleep disturbances, difficulty concentrating at work or in school, inability to work, significant itching and, at times, pain,” he noted.
According to Yu, there are two main types of contact dermatitis: irritant and allergic.
Irritant contact dermatitis, which accounts for 80% of all contact dermatitis, doesn’t involve an allergic reaction by the immune system, said Yu.
Instead, it happens when skin cells are damaged by exposure to irritating substances, such as solvents, detergents, soaps, bleach or nickel-containing jewelry. The condition is common in people whose professions involve daily use of chemicals, such as mechanics, custodians, health care workers or hairstylists.
Irritant contact dermatitis, however, can occur in anyone who is repeatedly exposed to potentially irritating substances. Diaper rash is a common form of the condition, with the rash caused by repeated contact with biochemicals in urine and stool.
Makeup, hair dye, nickel-containing scissors, belt buckles or clothes with metal snaps or zippers can also trigger reactions — as can over-washing hands with hot water and soap and wearing scratchy wool, said Yu.
Allergic contact dermatitis is a delayed allergic reaction that appears as a rash a day or two after skin is exposed to an allergen. “The most common example is poison ivy,” Yu said. “After exposure, the body generates a robust inflammatory reaction to the oils in the plant leading to an itchy rash within one to two days.”
Fragrances, nickel and the preservative thimerosal, which is found in some topical antibiotics, are also common causes of allergic contact dermatitis.
“The more people are exposed the allergen the more likely they are to develop contact dermatitis in response to that allergen,” Yu explained. “For example, people with body piercings have a higher likelihood of developing contact dermatitis in response to nickel compared with people who do not have them.”
Patients often think food is a trigger for allergic contact dermatitis, but Yu said what we eat is rarely the culprit.
“In reality, the cause is almost always contact with something in your topical products, whether this is shampoo, make-up remover, perfume, essential oil diffusers, paints, glues or a topical antibiotic,” he noted.
Dermatologists commonly prescribe steroids to treat symptoms of contact dermatitis, which can mimic several other skin conditions.
“It’s important to see a board-certified dermatologist to rule out other conditions, such as psoriasis, seborrheic dermatitis and atopic dermatitis,” Yu recommended.
Topical steroids may resolve itching and other contact dermatitis symptoms, but if the rash is widespread, dermatologists may prescribe a short-term course of oral or injectable corticosteroids.
Preventing future outbreaks depends on pinpointing—and then avoiding—the irritant or allergen that triggers flares. With irritant contact dermatitis, the trigger is usually easy to identify, as stinging, pain or discomfort usually happens within minutes of contact, said Yu.
For allergic contact dermatitis, knowing what to avoid often requires an in-office procedure called patch testing. This is when the doctor applies patches with small amounts of various allergens to the patient’s arm or back and then evaluates skin after about 48 hours.
Yu recommended finding a dermatologist with expertise in patch testing. For instance, dermatologists who are members of the American Contact Dermatitis Society (ACDS) are recognized experts in contact dermatitis and patch testing.