Balsam of Peru
Fragrance is the number-one cause of allergic contact dermatitis, and Balsam of Peru, a resin that is actually a conglomeration of scents, is often responsible. Because of its phototoxic ingredients, when the skin is exposed to sunlight, brown or reddish streaks called berloque dermatitis may occur wherever the scented product or perfume was applied—dermatologists report many incidents of berloque behind the ears. The key is to look for products that are totally fragrance-free — which is not the same as unscented. "Unscented means that a product can contain a masking fragrance to camouflage its pungent, unpleasant odor," says Bank. "Fragrance-free means truly no fragrances."
While most beauty products won't include this ultra-common makeup, skin, and haircare preservative on the ingredient list, many will have a formaldehyde-releasing agent like imidazolidinyl urea or quaternium 15, which can be equally reactive. Therefore, those who experience an allergy or irritation to formaldehyde actually have a list of names to be on the lookout for. Nowadays, two of the most frequent places where contact may occur are the nail and hair salon. "The most common cause of eyelid dermatitis is the formaldehyde in nail polish," says dermatologist Dr. Marsha Gordon. "After you polish your nails, there is a day or two when the finish is not rock hard, and that's when formaldehyde may be released. Your hands may not show redness because that skin is tough, but when you touch your eyes while washing or moisturizing, you can end up with dermatitis there."
They are the darlings of preservatives among mass manufacturers since they're cheap and stable. It can be downright difficult to find products that don't contain parabens like methyl, propyl, and benzyl hydroxybenzoate. Those who experience redness or a rash can avoid them entirely by seeking out lines such as Aubrey Organics, Burt's Bees, Dr. Hauschka, and Weleda, whose formulations are all paraben-free.
While the majority of acids — azelaic, alpha hydroxy, benzoic, lactic, sorbic — are tolerable in modest doses, cinnamic can pose a problem. A tartar-fighting agent in toothpaste, it can be the reason for itchy eruptions on the lips and around the mouth. Look for toothpaste without cinnamic acid (like Tom's of Maine), or if you're attached to a brand that has it, dermatologist Dr. Dennis Gross recommends applying Vaseline around the mouth and chin before brushing to form a barrier.