A skin allergy is when skin becomes irritated because the immune system reacted to something that is usually harmless. This is called an allergic reaction. An allergic reaction can cause rash, itching, burning, redness, bumps, hives, and swelling. Many different allergens can cause a reaction. Below are some of the most common allergic skin conditions:
- Atopic dermatitis (dur-muh-tahy-tis), or eczema, is when the skin becomes easily irritated, itchy, and dry. It is the most common allergic skin condition, and is more common in children than adults. Eczema is linked to both genetic (inherited from parents) and environmental factors. It is connected to asthma, food allergies, and seasonal allergies. Some things can make eczema flare up, such as certain foods, stress, soaps and lotions, or cold and dry air.
- Allergic contact dermatitis is when something touches the skin and causes a reaction. For example, some people are allergic to the metal nickel and will have a skin reaction if jewelry made with nickel touches their skin. A reaction to poison ivy is another example. Many people have an allergic reaction to the oil on a poison ivy or poison oak plant.
- Urticaria (ur-ti-kair-ee-uh), or hives, are raised bumps on the skin that form because of an allergic reaction. These bumps are also called welts or wheals. A person may get hives after eating a food they’re allergic to. The bumps are a result of histamine that the body releases in response to the allergen. Things besides allergies can cause hives as well, such as a bug bite.
- Angioedema (an-jee-oh-i-dee-muh) is swelling deep in the skin. It often happens on places like the eyelids, lips, and throat, and often happens together with hives.
The symptoms of a skin allergy vary depending on the type of reaction:
- Eczema causes an itchy, scaly, red, dry rash, especially on the face, hands, elbows, and knees. Sometimes eczema weeps clear fluid as well.
- Allergic contact dermatitis causes a rash that may be itchy but is often painful. The rash may have both raised bumps and blisters. The reaction may happen right away or it may be up to 48 hours after your skin was exposed to whatever is causing it to react.
- Hives are raised, flat, itchy bumps that may also be tender. Hives are a sign of a potentially serious allergic reaction.
- Angioedema is a type of swelling. For example, angioedema on the eyelid can cause your eye to be swollen shut. When it happens in the throat, it is an emergency because the swelling makes it hard to breathe.
Hives and angioedema may be signs of a serious allergic reaction. Call 911 or go to the emergency room if:
- You have hives all over your body
- You are starting to have trouble breathing
See a doctor if:
- You need help with controlling your eczema symptoms
- Your rash is bleeding or has yellowish pus and looks infected
- You think you may have an allergy that you didn’t have before
- You have a skin rash that doesn’t get better after 2 to 3 weeks
To diagnose a skin allergy condition, your doctor may:
- Ask questions about your skin, symptoms you are having, and when it happens.
- Examine your skin. The doctor may also look at your eyes, nose, throat, and chest to check for signs of an allergy.
- Recommend allergy testing:
- Skin prick test. If the doctor suspects you may be allergic to something, the doctor or nurse will put a bit of it on your skin and then lightly scratch the skin. If your body reacts to it, you will usually have a rash, redness, and itching within 15 minutes. You may also see a hive. This suggests an allergy, especially if the hive is large. Your skin can be irritated by things that it’s not allergic to, so the skin prick test is just one piece of information for you and your doctor. It doesn’t necessarily mean you have an allergy even if your skin reacted.
- Intradermal (under the skin) skin test. This test is used if the skin prick didn’t cause a reaction, but the doctor still suspects you have an allergy. For this test, a doctor or nurse injects some of the allergen into your skin and checks the reaction after a certain amount of time.
- Blood tests (specific IgE). The doctor takes a sample of blood and sends it to the lab. The lab will put the suspected allergen into your blood and check for IgE, which your blood makes to attack the allergens. Unfortunately, this test is not always reliable because it will often show that there is allergy when, in fact, there isn’t one. This is called a “false positive.”
- Challenge test. While you are in the doctor’s office, you inhale or eat a small amount of allergen so the doctor can see if you react. The doctor is there to observe and help in case you have a life-threatening reaction. This test is used to check for allergic reactions to food or medicine.
- Patch test. This test checks for allergic contact dermatitis. The doctor puts a small amount of allergen on your skin, covers it with a bandage, and lets it sit for 2 to 4 days. The doctor checks for signs of a reaction — usually a rash right under the bandage.
Treatment for skin allergy varies depending on the problem and the allergen, but usually includes two approaches:
- Avoid the allergen, if it is known
- Use medicines, creams, and other strategies to relieve the itching, swelling, or pain
Below are some recommendations for treating each of the allergic skin reaction types.
- Avoid rubbing , scratching, or scrubbing the skin
- Moisturize the skin several times a day with an ointment or lotion that has no alcohol, fragrance, or dye. Use this lotion or ointment after you bathe when the skin is still damp.
- Avoid putting wool or lanolin on the skin. Lanolin is in some skin products.
- Use gentle soaps and shampoos.
- Take short baths or showers, and make sure the water is not hot. Lukewarm water is gentler on the skin.
Hives and Angioedema
- For acute (sudden) hives and swelling a, an antihistamine (like Benadryl®) can stop the allergic reaction. In the future, try to avoid the allergen that caused the reaction. Carry medicine, such as an EpiPen, if you know you have severe allergic reactions to something.
- The cause of chronic (ongoing) hives and swelling is unknown. For some people, alcohol, aspirin and other nonsteroidal anti-inflammatory medicines (NSAIDs) can trigger a reaction. Try to understand your triggers and avoid them. It also helps to keep the skin cool and avoid tight clothes. Antihistamines are the most common medicines used to treat hives.
Allergic Contact Dermatitis
- A skin reaction from allergic contact dermatitis will go away, but usually takes from 14 to 28 days.
- If you come in contact with something that can cause allergic contact dermatitis (like poison ivy), scrub the skin with soap and water right after.
- The doctor may give you an antihistamine or cortisone medicine to take to help the rash heal. It will still likely take at least a couple weeks for the rash to go away.
- Calamine lotion and cool compresses can relieve some of the itching and pain. Lukewarm oatmeal baths can also soothe the skin.
The best way to prevent allergic skin reactions is to try to find out what allergen causes the reaction and avoid it. Consider potential allergens that go directly on the skin, such as soap, shower gels, hair products, makeup, lotions, and deodorants. Foods and medicines can also cause allergic reactions, especially hives and swelling.
For eczema, keep the skin moisturized and avoid the things that cause the eczema to flare up.