After fragrance, the next most common source of contact dermatitis, as a class, is preservatives, and the most common preservative is paraben.
The woman, as Dr. Marks suspected, turned out to be allergic to cocamidopropyl betaine, an ingredient in baby shampoo. She had been advised by an ophthalmologist to bathe her eyelids in baby shampoo to avoid stinging, but the effect was inflammation and scaling.
Dr. Marks, professor and chair of the department of dermatology at the Milton S. Hershey Medical Center, Penn State University, is an authority on cosmetic contact and photosensitive dermatitis, and he gets referrals from several states.
Like most of the patients at his clinic, the woman had patch tests for 100 or more allergens. She was positive for cocamidopropyl betaine.
None of the allergic contact dermatitis causes is common, but the two most common are fragrances and preservatives, he points out, followed by hair- and nail-care ingredients and sunscreens. The allergens may sneak up on patients in odd ways.
If Dr. Marks sees lip dermatitis or cheilitis, he thinks toothpaste.
"One of the first things I think of is allergy to fragrance in tartar-control toothpaste, which has an increased amount of fragrance to mask the bitter taste of the tartar-control ingredient," he says. "Usually the doctor and the patient don't know or suspect the cosmetic that is causing it," Dr. Marks adds. For instance, there are more than 1,000 fragrance ingredients.
For fragrances he uses at least two patch screens. The standard fragrance mixture picks up perhaps 75 percent of the allergens, and Myroxylon pereiae (Balsam of Peru) catches some 50 percent. So often these two screens aren't enough.
"I do both and actually a lot more," he says.
The source of allergens has evolved with the market. In the 1980s, for instance, musk ambrette was a common cause of photoallergenic contact dermatitis from fragrances, but it is no longer a popular ingredient in men's cologne.
In Dr. Marks' presentation he showed a photo of Bill, a 60-year-old man who had been treated with steroids for a year for neck and facial dermatitis. He showed positive results in patch tests to a fragrance in his shaving cream and to the preservative quaternium-15 in a moisturizer. Bill's dermatitis cleared by avoiding the fragranced shaving cream and the moisturizer containing quaternium-15.
After fragrance, the next most common source of contact dermatitis, as a class, is preservatives, and the most common preservative is paraben, which, when mixed with water, can preserve moisturizers such as lotions, creams or ointments.
Quaternium-15 is a formaldehyde-releaser. Sensitivity may be to quaternium-15 or to the formaldehyde it releases, Dr. Marks says.
There are more than 15,000 products with paraben as a preservative, with about 2 percent of patients allergic to paraben, according to the North American Contact Dermatitis Group's results. But the preservative ingredient quaternium-15, used in 600-plus products, has a several-fold higher rate of allergenicity.
Though less common, hair and nail products can cause problems as well, Dr. Marks says.
Women may be allergic to tosylamide/formaldehyde resin in nail polish, and they can cause facial, chest and neck dermatitis by touching these areas with their polished fingernails. Some women are allergic to the ethyl acrylate used in creation of sculptured nails.