Like HowStuffWorks on Facebook!

Allergy Basics


Skin Allergies

The skin is your largest organ and an important defender against invaders. It is constantly bombarded and usually fends off trouble quite successfully. Sometimes, however, an allergen gets the best of your skin, causing a reaction. This section will explore skin allergies and the reactions they cause.

Skin Allergy Symptoms

Symptoms can include a rash or hives, or swelling, itching, and cracking of the skin. Our hands, arms, neck, and face come in contact with so many substances every day that they are the most common sites for an allergic skin reaction, but no part of your anatomy is immune. A skin reaction that is the result of contact with an allergen is called allergic contact dermatitis. (By contrast, a skin reaction caused by contact with a substance that is harsh or caustic is called irritant contact dermatitis and does not involve allergies or the immune system.)

What Causes Contact Dermatitis?

Potential allergens exist everywhere. Many can be rounded up in the bathroom cabinet: nickel/chrome in jewelry and snaps; latex found in condoms, rubber gloves, bandages, and rubber bands; chemicals in cosmetics, toiletries, and perfumes; hair products, including hair dye; and laundry detergent and fabric softeners. The great outdoors hosts such potential villains as poison oak, poison sumac, and poison ivy.

Identifying the exact cause of allergic contact dermatitis can be difficult because your skin comes in contact with hundreds of suspects a day and first reactions may occur hours or days after the initial contact. In some cases, a reaction doesn't occur until weeks or months of prolonged use. Luckily, contact dermatitis isn't named contact for nothing. Many allergens leave a trail to follow. The location of the rash, hives, or itch will help you to put the suspects in a lineup.

For example, let's say your ears itch. What comes in contact with them? Earplugs, headphones, earrings, perfumes, hair products, and lotions might be major suspects.

How about a rash that develops under your arms? The possible causes: lotion, deodorant/antiperspirant, elastic straps in clothes, a bra's underwire, new fabrics, etc. Like so much in the allergy world, a little observation can go a long way toward discovering what is irritating you.

Pinpointing and avoiding contact with the allergen is the primary treatment for allergic contact dermatitis. However, if the rash spreads or if you develop hives or experience uncontrollable itching and the skin becomes red, tender, and damaged, see your physician.