Looking for Sources of Rashes, Allergies

Substances from your favorite makeup to the zipper on your clothes can cause itchy rashes and contact dermatitis.

Contact dermatitis can be induced by substances that either trigger allergies or irritate the skin, according to an article in the current issue of Redbook, and the resulting rash can occur anywhere on your body, from the scalp on down.

“When an allergy is involved, your immune system perceives the substance touching your skin to be a threat,” said dermatologist Dr. John Romano of the New York Hospital-Cornell Medical Center in New York City. “In response, antibodies initiate the release of certain chemicals in the body, most commonly histamines, which cause an allergic reaction.”

Usually, first exposure causes an allergy reaction, but sometimes a reaction may occur only after re-exposure to the allergen at a later date--sometimes years later.

Doctors can usually distinguish contact dermatitis from other types of skin problems by its unusual configuration, according to Dr. Steven Victor of Lenox Hill Hospital in New York City.

“Eruptions often have clear-cut margins and geometric outlines,” he said, “although they can sometimes show up as lines or groups of blisters.”

Here’s where contact dermatitis most often shows up and the suspects to consider:

Scalp, hairline, forehead, face and neck. Chemicals in shampoo, hair spray and hair-color products all can affect the skin in these areas. Thickeners, foam stabilizers, fragrances and preservatives are the usual allergens in shampoo. Permanent and semi-permanent hair dyes also contain substances that can cause allergic reactions in some people.

Facial dermatitis also can be triggered by allergies to lanolin, wood alcohols, Vitamin E, fragrance, propylene glycol, and preservatives in foundations and face creams.

Perfumed facial tissues can cause a rash, as can makeup sponges made of rubber and rubber bathing caps.

“These substances are among the most widespread causes of allergic contact dermatitis,” Victor said.

One of the most common culprits in neck rashes is nickel, an allergen often found in jewelry, including sterling silver and 14-, 18- and 24-carat gold. And, the formaldehyde in nail polish is a major culprit in eyelid dermatitis.

“The polish can even trigger problems when it’s completely dry,” Victor said.

Products that cause rashes in the face and scalp areas can cause rashes in the ear areas as well. Nickel in earrings and nickel or plastic in eyeglass frames also can be a culprit.

Chest, stomach, back, arms and legs: The fragrances in perfumed soaps can cause rashes, as can nickel in zippers, buttons and snaps. Chemicals used in manufacturing clothing and sheets are also troublemakers. The rubber in waistbands of cotton underwear can cause trouble if you bleach the underwear.

One surprising source of trouble is ordinary house and garden plants, including chrysanthemums, tulips, daisies, philodendrons, daffodils, hyacinths, narcissus, magnolias, tea roses, lilies and poinsettias.

Medicines also can cause allergic reactions. A prime offender in dermatitis is the topical antibiotic neomycin. A reaction can occur whenever it is applied.