Rethink “Standard” Advice to Patients with Allergies

Patients with allergic contact dermatitis often leave the dermatology clinic with a list of instructions and sometimes complicated strategies to avoid contact with known or suspected allergens. One piece of advice may be obsolete: Patients with fragrance allergies may not have to avoid scented laundry detergents after all.

New evidence confirms the growing suspicion that fragrance chemical residues left on fabrics do not elicit immediate or delayed allergic reactions in previously sensitized patients.

The newest data, which appear in the June issue of Contact Dermatitis, involve dose-response and fabric patch tests in 36 patients with previous positive patch reactions to two popular chemical fragrances. At a dose of 20 times the estimated exposure levels anticipated from washed fabrics, two of 36 patients reacted to fragrance. No patient reacted to lower levels. Results of the patch tests showed that 18 subjects reacted to vehicle alone, while 20 reacted to vehicle in combination with fragrance. Reactions were minor, nonspecific skin reactions.

One source of allergens that still warrants concern is shampoo. When presented with an unusual outbreak on the face, keep possible contact allergy to shampoos in mind. Shampoos are a frequent source of contact allergy, which often manifests on the face, due to chemicals washing down the face during the rinse phase.

According to a recent review (Dermatitis; 20(2):106-10), the allergens most commonly present in shampoos, in order of prevalence, are: fragrance, cocamidopropyl betaine, methylchloroisothiazolinone/methylisothiazolinone, formaldehyde releasers, propylene glycol, vitamin E, parabens, benzophenones, iodopropynyl butylcarbamate, and methyldibromoglutaronitrile/phenoxyethanol. Patch testing can identify a sensitizing chemical.