Eczema patients should be advised to treat their skin with ointments, which are unlikely to contain antimicrobial preservatives.

People with eczema are especially vulnerable to allergic reactions to certain preservatives in lotions and creams, according to a new study.

With eczema, the skin does not function as a barrier the way it normally would, said senior author Donald V. Belsito, a dermatologist at Columbia University Medical Centre in New York City.

People with eczema often apply lots of moisturisers and topical medications to combat dryness and itchiness, Belsito said.

“The more exposure, the more likely you are to develop an allergic reaction to a chemical,” he told Reuters Health.

In his study published in the Journal of the American Academy of Dermatology, patients with eczema were more likely to have allergic reactions to several cosmetic preservatives, called formaldehyde releasers, than people without eczema.

Of 2,500 people tested for allergic reactions in the study, 342 had eczema. After a battery of individual allergy tests, the eczema group was more likely to have a reaction to preservative chemicals quaternium-15, imidazolidinyl urea, DMDM hydantoin and 2-bromo-2-nitropropane-1,3-diol.

Many things might cause these chemicals to be harmful, Belsito said. One possibility is that this group can penetrate the outer layer of skin and bind to immune cells, activating them. All of the chemicals in this group also release formaldehyde.

Eczema patients in the study did not seem to be predisposed to allergies to parabens, formaldehyde or diazolidinyl urea, which are not formaldehyde releasers.

It is unclear what makes the formaldehyde releasers problematic, the authors write. It could be that those products are more commonly used, so people with eczema have more exposure to them and more opportunity to develop a reaction.

About eight per cent of all people have irritation or allergic reaction to formaldehyde itself, according to a previous study.

These are not dangerous allergic reactions, just very uncomfortable, like poison ivy, Belsito said.

Skin reactions usually go away if you stop using the product and see your doctor, who may give you a steroid cream, said Michael Dyrgaard Lundov, a senior researcher at the National Allergy Research Centre in Copenhagen, Denmark. He was not involved in the new study.

Eczema – which is an excessive immune response similar to those in asthma and allergic reactions – causes painful, red scaly patches on the skin. It’s becoming more common, Belsito said, and in some areas up to 30 per cent of kids have it.

Some people with mild eczema haven’t been diagnosed – they just think they have sensitive skin, he said.

Eczema patients “should be advised to treat their skin with ointments, which are unlikely to contain antimicrobial preservatives,” he said.

Micro-organisms need water to proliferate, Lundov said. Products without water, like ointments, therefore do not need to include antimicrobials.

Skin reactions usually go away if you stop using the product and see your doctor, who may give you a steroid cream

Eczema patients should also avoid products with fragrance, which can cause irritation as well, he said.

If eczema patients must use creams or lotions containing antimicrobials, they should choose products preserved with parabens, Belsito and Lundov agreed.

Parabens are one of the most common cosmetic preservatives, in use for more than 70 years, according to the US Food and Drug Administration. Less than one per cent of people had a reaction to parabens in a previous study.

Allergic reactions depend on how potent a chemical is, how often you are exposed, how much of the chemical is in the product you use and the unique tolerance level of your own skin, Lundov said.

“Despite the massive use of parabens in cosmetic products, the parabens are rarely a cause of allergic contact dermatitis,” Lundov said. “This is because it is not a very potent allergen.

“Quaternium-15 and the other formaldehyde releasers are used in lower concentrations and fewer products, but is still a bigger problem because the releaser itself and the released formaldehyde are more potent allergens than the parabens,” he said.