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Contact Dermatitis: Facts About Skin Rashes

You call it a rash. Your doctor calls it dermatitis. Either way, it happens when your skin gets inflamed after it comes in contact with something.

Contact Dermatitis Causes

Your rash could be caused by an allergy, or by damage to your skin.

If it’s caused by an allergy, your immune system is involved. After your skin touches something, your immune system mistakenly thinks it’s under attack. It springs into action, making antibodies to fight the invader. A chain of events takes place that causes a release of chemicals like histamine. That’s what causes the allergic reaction -- in this case, an itchy rash. It’s called allergic contact dermatitis.

Usually, you won’t get a rash the first time your skin is touching something you’re allergic to. But it sensitizes your skin, and you have an allergic reaction the second time your skin touches it. If you get a rash the first time, chances are you were exposed to the allergic trigger before and just didn’t know it.

Allergic Reaction Triggers

  • Poison ivy, poison oak, and poison sumac
  • Hair dyes or straighteners
  • Nickel, a metal found in jewelry and belt buckles
  • Leather (chemicals used in tanning leather)
  • Latex rubber
  • Citrus fruit, especially the peel
  • Fragrances in soaps, shampoos, lotions, perfumes, and cosmetics
  • Some medications that are applied to the skin

When Skin Damage Causes a Rash

Some rashes look like an allergic reaction but really aren’t because your immune system isn’t involved. Instead, you touched something that directly hurt your skin. The longer that thing stayed on your skin, the worse the reaction. It’s called irritant contact dermatitis.

If you have eczema, you’re more likely to get this kind of a rash.

Telling Rashes Apart

It’s not easy to tell whether your rash was caused by an allergy or by damage to your skin, because many of the symptoms can be the same.

  • With an allergy, symptoms are usually right around where you touched the thing you’re allergic to. A rash from skin damage may be more widespread.
  • You’ll usually see a rash immediately if something is irritating or damaging your skin. With an allergy, it may be a day or two before the rash shows up.
  • In both cases, your skin may blister, or you may get a raised red rash.
  • Your skin will itch and maybe burn. Irritant contact dermatitis (skin damage) tends to be more painful than itchy.
  • A rash on your hands can be a tell-tale sign of skin damage, because your hands are exposed to so many substances.

When to See Your Doctor

Call your doctor if your rash isn’t better after a couple of days. Usually your doctor can examine you and ask questions to figure out what’s causing the rash.

Depending on how severe your rash is, your doctor may prescribe steroid pills or ointment, and an antihistamine.

Treating a Rash at Home

  • Don’t touch the thing that caused the rash.
  • If you can wash your skin with mild soap and cool water right after exposure, you may get rid of all or most of the problem substance. That will help reduce symptoms.
  • For blisters, try applying cold moist compresses for 30 minutes three times a day.
  • Oral antihistamines can help relieve itching.
  • Don’t use an antihistamine lotion unless suggested by your doctor, because it sometimes can cause skin irritation or an allergic reaction.
  • If the rash covers only a small area, a hydrocortisone cream may be all you need for relief.

WebMD Medical Reference

Reviewed by Laura J. Martin, MD on October 31, 2012

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