ATLANTA (FRONTLINE MEDICAL NEWS) – Formaldehyde has various clinical presentations and variable thresholds to trigger allergic contact dermatitis, so it requires a high index of suspicion, according to Salma de la Feld, MD.

It may present as irritant contact dermatitis, allergic contact dermatitis (especially to the hands and face), airborne allergic contact dermatitis, or systemic allergic contact dermatitis (to aspartame).

In 2015 the American Contact Dermatitis Society named formaldehyde, an antimicrobial preservative, the Allergen of the Year , and it currently ranks as the ninth most common allergen. Part of that stems from the fact that formaldehyde can be released from several different chemicals, Dr. de la Feld said at the annual meeting of the American Academy of Allergy, Asthma, and Immunology.

From most-releasing to least-releasing, these chemicals include quaternium-15, diazolidinyl urea, DMDM hydantoin, imidazolidinyl urea, and bronopol. Exposure can come from personal care products, prescription topical steroids and acne creams, Brazilian hair keratin, cigarettes, and textiles made of blended fabrics, as well as occupations such as a leather handler, surgical nurse, pathology lab worker, and hairdresser.

“Patients can be allergic to either the formaldehyde that [a product] releases or the non–formaldehyde component or both,” said Dr. de la Feld, who is a dermatologist at Emory University, Atlanta.

Recent studies suggest that the formaldehyde allergen should be tested at 2% instead of at 1%. “You do get a few more irritant reactions [with this approach], but you’re also going to catch more people who have a true positive reaction,” she said. “If you see a borderline papule with a little pink, that might be an irritant. You want to test for the formaldehyde releasers. When you do have a positive reaction, you want to have a high index of suspicion. Patients have to be strict in what personal care products they’re using. Some people might be able to tolerate a low concentration of formaldehyde in some products and that magic number differs between patients.”

From a treatment standpoint, Dr. de la Feld advises patients to avoid all formaldehyde releasers and to wear 100% fabrics in an effort to steer clear of textile exposure. “I like to have people be really strict [in their avoidance] when they’re first starting out,” she said. “They don’t like it, but I’ll say, ‘You’re so itchy. Let’s start really strict to get you clear and better.’ Once they’re better and there’s that one moisturizing cream that they really love, then [you] can do a repeat open application test. If nothing happens, it’s probably safe. If [they] start getting red and itchy there, [they] should probably throw away that moisturizer.”


Fragrance, which was named Allergen of the Year in 2007, is another common contact allergen. An estimated 4%-11% of the worldwide population is allergic to fragrance mix, while 1.6%-10.8% is allergic to balsam of Peru. T.R.U.E. tests for the allergen often yield false-negative results. Clinicians who fail to test for fragrance mix 2 will miss about one-third of fragrance allergic contact dermatitis diagnoses. “If the distribution is scattered, you want to be suspicious for fragrance allergy,” Dr. de la Feld said. “Sometimes patients get exposed inadvertently by their significant other or by a family member who is spraying a fragrant product.” Treatment is avoidance. “You want to tell patients to look for products labeled as fragrance free,” she said. “ ‘Unscented’ does not count. When patients tell you that they’re not using any perfume, you want to ask them if they’ve put any on their clothes.”

Systemic contact dermatitis

Dr. de la Feld finished her presentation by discussing systemic contact dermatitis, which she defined as a rash from systemic exposure to an allergen in someone who was previously sensitized. Alternative names for the condition include endogenous contact eczema, systemically-induced contact dermatitis, and internal-external contact-type hypersensitivity. She acknowledged that not all dermatologists believe systemic contact dermatitis to be a true clinical condition, but she does.

“It’s most classically and commonly reported with nickel and balsam of Peru and more slowly with some other allergens,” she said. “It can have multiple clinical presentations, and it’s not always widespread.” The three most common presentations are dyshidrotic hand eczema, sites of prior contact dermatitis (from contact or patch test), and anogenital and/or flexural areas (Baboon syndrome). There are other reports of systemic contact dermatitis presenting as disseminated patchy dermatitis, generalized erythroderma, cheilitis, and lichen planus of the lip.

Dr. de la Feld reported having no relevant financial disclosures.