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Signs of Allergies

A rash is a change in the normal appearance or feel of your skin. A rash may be painful or itchy, and it might make your skin red, bumpy, dry, cracked, blistered, swollen or warm. A rash can be caused by many different things, like a food allergy to milk or eggs or an infection. Sometimes it’s hard to know whether your rash — including welts or bumps, itching or redness — are signs of an allergic reaction or something else.

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Common Skin Rashes

Eczema, contact dermatitis and hives are three common kinds of skin rashes that may be related to allergies.


Eczema (also called atopic dermatitis) frequently appears as dry, red, cracking and itchy skin. If you have eczema, you may also experience small bumps that ooze a clear or yellowish fluid.

Contact Dermatitis

Contact dermatitis is an allergic skin reaction to an irritant or allergen. The reaction can appear as a rash, blisters, burning or itching.


Hives (also called urticaria) are red, itchy welts or bumps that don’t usually last long. Hives lasting less than six weeks (acute urticaria) are usually caused by an allergic reaction or a viral infection. They may appear on different parts of the body but usually last 24 hours or less.


Eczema flare-ups can be triggered by contact with allergens like animal dander, irritants like coarse fabric, or household products like detergents and cleaners. Being too hot, too cold, stressed or ill can also trigger an eczema outbreak.

Contact dermatitis can be triggered by skin contact with a variety of allergens or irritants. Plants like poison ivy, poison oak and poison sumac are common triggers. Household products like hair dyes, cosmetics, soaps and lotions can also trigger contact dermatitis. If you’ve experienced sensitivity, try avoiding products with strong fragrances or chemical smells. Nickel, a metal commonly found in jewelry, is another common material that can cause an allergic reaction. Natural rubber latex, leather and medications that you put on your skin, can also be triggers.

The sun can also cause a skin rash when interacting with cosmetic or skin products. This is not a sun allergy, but if you develop a rash in the sun after using products like shaving lotion, sunscreen or perfume, you may be experiencing photoallergic contact dermatitis.

Hives can be triggered by insect stings or bites; contact with allergens like latex, chemicals, animals, plants or cosmetics; or ingestion of foods or medications. Cold, heat, pressure, sweating, vibration (from running, snoring, clapping, etc.), sunlight and water can also be triggers.

It can be difficult to identify what triggered your rash. Allergists are trained specialists who can help you identify the source of your allergic reaction and develop a treatment plan to help you find relief.

Learn about common triggers and how to avoid them. Here are examples:

  • Food. Peanutseggsnutsmilkshellfish
  • Medications. Antibiotics such as penicillin, aspirin and anti-inflammatory drugs (NSAIDs), opiates, cancer therapies
  • Topical contact. Latex, chemicals, animal or plant proteins, cosmetics
  • Insect bites and stings. Bees, wasps, hornets, yellow jackets, fire ants
  • Physical or environmental factors. Cold, heat, pressure, sweating, vibration, sunlight, water
  • Viral infections.

How to Get Tested

Many irritants and allergens can cause itchy and uncomfortable skin rashes. Getting tested by a board-certified allergist can help you identify your specific triggers and find relief. Your allergist will review your symptoms and take a detailed medical history to identify likely causes before beginning your tests.

Allergy testing is the first step in getting allergy rash treatment. Skin testing is fast and accurate, and it is considered the gold standard for allergy testing. If you have severe eczema or are on certain medications, your allergist may conduct blood testing in addition to or instead of skin testing.

Your allergist will use your medical history and your test results to identify specific triggers and how to treat your allergy symptoms, and help you find relief.

It Could Also Be…

It can be difficult to identify the cause of skin rashes. If you also have a fever, talk to your doctor about possible bacterial or viral infections.

If your allergist rules out allergies, ask what else might be causing your skin rash, such as:

  • Bug bites or stings
  • Cellulitis
  • Chickenpox
  • Fifth disease
  • Lupus
  • Lyme disease
  • Measles
  • Mononucleosis
  • Ringworm
  • Shingles
  • Staph infection