What can set off an allergic skin reaction? Some unusual suspects are wrinkle-free clothing, spinach salads, plywood, tires, and Italian food, according to dermatologist Jennifer H. Perryman, MD.

Here’s a closer look at the allergens highlighted by Dr. Perryman in a presentation at Skin Disease Education Foundation’s Women’s & Pediatric Dermatology Seminar:

Formaldehyde: It’s everywhere

“In general, formaldehyde is found on everyone in this room in two different places: preservatives in skin care products and in a lot of our clothing,” said Dr. Perryman, who practices in Greeley and Fort Collins, Colo.

The preservative is used in an even wider variety of products, including fluids used in industry (such as metalworking) and topical medications. But people are especially likely to encounter it in clothing – via formaldehyde textile resins – as well as in cosmetics, soaps, and lotions.

On the clothing front, Dr. Perryman said, formaldehyde textile resins have been used since the 1930s. They’re used to treat blends of synthetic and cotton fibers and bed sheets. Beware of “wrinkle resistant” and “permanent press” clothing (although not all have been treated with this resin). “Newer formaldehyde textile resins have less formaldehyde release, but they may be more expensive, and some industries may not use them,” she said.

Avoiding formaldehyde textile resins isn’t a simple matter.” You have to go out of your way to stay away from a polyester-cotton blend,” she said. “And don’t forget bedsheets,” she added, noting that the packaging on some sheets include information about cotton count, “but when you flip over the label it says it’s ‘50% cotton and 50% polyester or other.’ ”

Some patients will bring their own bedsheets to hotels so they don’t experience flares from hotel bedsheets, she added.

Other products can trigger this skin allergy. Beware, Dr. Perryman said, of formaldehyde exposure from paper, cardboard, cigarette smoke, processed wood products like plywood, foam housing and industrial insulation, embalming fluid and tissue fixatives, and some paints and adhesives.

What are the signs that someone may have a case of formaldehyde allergy? It may cause patchy generalized dermatitis, erythroderma, and nummular dermatitis. It may spare the hands, feet, and face because those parts of the body have less exposure to clothing, and it’s likely to especially affect body areas where clothing is tight. And for unknown reasons, this allergy is more common in the elderly, Dr. Perryman said.

Textile dye: Beware polyester

This allergy is mainly triggered by synthetic fabrics like polyester, rayon, and acetate, she noted. Darker colors are more allergenic. Clothes made of natural fibers such as cotton, silk, linen, and wool are alternatives. These are not dyed with these dyes, she said, adding that a reaction to wool will be from irritation, not from the dye.

Paraphenylenediamine: Keep an eye out for this dye ingredient

Paraphenylenediamine, which can trigger allergic reactions, is found in leather dye, fur dye, and some (but not all) hair dyes. Be aware that it can cross-react with other allergens like sulfonamide medications.

If a patch test turns up a reaction to “Black-Rubber Mix,” which includes paraphenylenediamine, consider whether the patient has exposure to the rubber in tires. Car mechanics may be affected by this allergy, Dr. Perryman said.

Neomycin: A drop of trouble

Allergy to the antibiotic neomycin can be triggered by exposure to gentamicin and tobramycin eye drops. Patients may believe they have an infection, Dr. Perryman said, so consider getting a culture. In some cases, an allergic reaction to neomycin may be incorrectly diagnosed as cellulitis.

Nickel: Not just a jewelry hazard

Jewelry and coins can trigger nickel allergies, but be aware that systemic nickel allergy can also trigger skin problems from a patient’s diet. It may be necessary to put patients on a low-nickel diet that avoids foods such as healthy grains, greens (especially spinach), nuts, legumes, and chocolate. “I always feel bad” putting patients on a restrictive diet, Dr. Perryman said, but it can be helpful to take 500 mg of vitamin C three times a day since it binds to nickel.

Cobalt: Watch the chocolate and coffee

Jewelry with cobalt can cause an allergic reaction. Dr. Perryman tells patients to buy an inexpensive “spot test” product online that detects whether jewelry has nickel or cobalt. Cobalt allergy can also trigger symptoms in patients exposed to “hard metal” industrial tools, cement, and masonry. Workers in the plastics and dye industries may be exposed too.

Like nickel, Dr. Perryman said, systemic cobalt allergy related to diet is also possible. The list of foods that contain higher levels of cobalt is long, and includes apricots, beans, beer, chocolate, coffee, nuts, tea, and whole-grain flour.

Dr. Perryman also mentioned several other allergens to keep in mind:

  • Chromate can trigger reactions in people who wear leather shoes (the metal can be used in tanning). It can also cause problems in workers exposed to it via cement, bricks, drywall, and metal plating.
  • Chromium picolinate, an over-the-counter supplement, can cause systemic dermatitis.
  • Gold in jewelry can trigger an allergic reaction. Talk to patients about replating their jewelry, Dr. Perryman said.
  • Rubber can trigger reactions due to exposure to rubber bands, makeup sponges, and rubber gloves (even nitrile ones). Be aware that both rubber and latex allergies may coexist and consider a blood test for latex allergy.
  • Systemic balsam allergy related to an individual’s diet is possible. Tomato is an especially big villain on this front, along with citrus fruits, spices, cola, chili, and chocolate.

Dr. Perryman disclosed consulting work for IntraDerm. SDEF and this news organization are owned by the same parent company.