If you’ve endured the intense itching and irritation of eczema, you may long to know: What’s triggering my flares? While it’s not fully clear what causes eczema, a form of atopic dermatitis (AD), there are several common triggers ranging from overly dry skin to allergies. “Eczema and allergies often co-exist, and without eliminating an allergen trigger, or treating its symptoms, the eczema may not fully improve,” says Martin Smith, M.D., a double board-certified allergist and immunologist at The Cleveland Clinic in Cleveland, OH.

Addressing both eczema and allergies can be mutually beneficial, says Charlie Dunn, M.D., a board-certified pediatrician and dermatologist at Advanced Dermatology and Cosmetic Surgery in Orlando, FL. “By understanding any underlying allergies, we can tailor a more effective treatment plan, leading to better overall control of eczema,” he says. And repairing and strengthening the skin barrier, which is damaged in eczema, may be good for your allergies, too. “A healthy skin barrier acts as a first line of defense against environmental allergens.”

So, should everyone with eczema get tested for allergies? And what’s the best way to do that? Moreover, what’s the difference between allergies and sensitivities, and how can each affect your eczema? Find these answers and more in your guide to everything you need to know about allergy testing for eczema, as well as next steps to help shift your system out of reactive mode.

Eczema and Allergies Link

The Eczema Allergy Overlap

Not everyone with eczema also has allergies, but there is definitely overlap between the two health conditions. Babies born into families with a history of allergies or asthma are at a higher risk of developing eczema, according to the American College of Allergy, Asthma, & Immunology (ACAAI). And little ones with eczema are more likely to get food allergies, asthma, and hay fever, in what is known as the “atopic march” or “allergic march.”

Consider this: Young kids with eczema are more than six times as likely as kids without it to develop food allergies, according to the National Eczema Association. “This is due to their inflamed and ‘cracked’ skin barrier, which allows food proteins to enter through the broken skin,” says Dr. Smith.

This can lead to “sensitization,” a process in which the immune system produces allergic IgE antibodies to these foreign food proteins. Sensitization can lead to a food allergy emerging in some, but not all, kids. “Studies have shown that treating eczema early with emollient creams and systemic medications such as the injectable dupilumab may decrease a child’s risk of developing other allergies and halt the progression of the atopic march,” he says.

Despite the known connection, experts don’t recommend blanket food allergy testing for all babies and young children with eczema. “While some children with severe eczema may benefit from food allergy testing and potential removal of specific foods from their diet (peanut, egg, and milk are the most common food allergies identified in these children),” Dr. Dunn says, “it is not recommended to test all children with eczema for food allergies due to the high rate of false positive results, which leads to misdiagnosis and unnecessary food avoidance.”

Who Should Get Tested?

Do I Need Allergy Testing for My Eczema?

If you only have an occasional patch of itchy skin, you might not need allergy tests. “I usually recommend allergy testing for people with severe eczema that affects more than 10% of their body, or eczema that’s not responding well to therapy,” Dr. Smith says. (Eczema therapies include over-the-counter and prescription topical medications, as well as oral and injected medications.)

If you’ve already been diagnosed with allergies, you should let your allergist know if you notice skin changes to see if they want to adjust any of your medications or consider something more aggressive, like allergy shots.

Overall, you’re best being proactive about looking into allergies, says Purvi Parikh, M.D., an allergist and immunologist in New York and clinical assistant professor in pedicine and pediatrics at New York University School of Medicine in New York City. “If your eczema can’t be controlled with a moisturizer, book a visit with an allergist, to evaluate if you need allergy testing and any treatments.” If you are wondering if you should see a dermatologist or an allergist for allergy testing, there are some tests only allergists do, but some both can do.

What to Expect

IgE Allergy Tests, Explained

At your allergy appointment, your first step will be to share your health history, says Dr. Smith. “This can clue us into what is causing the eczema to flare,” he says. “If, for example, your eczema flares after visiting a friend’s house who has pets, then we know we should test for pet allergies. If eczema flares at night and is worse after someone has been sleeping, then we can think of testing for dust mites.” If there is no rhyme or reason to the eruptions, you may be tested with a panel for a range of allergens.

Allergy blood tests are called IgE tests, which means they check for antibodies called immunoglobulin E (IgE) produced by the immune system.

When it comes to testing for food allergens in particular, “less is more,” says Dr. Smith. “We know that people can have positive [immunoglobulin E] IgE blood tests but have no clinical reaction when they ingest that food”–so they can safely eat them. But if you notice your eczema flares after you have peanut butter or edamame, say, getting allergy tests would be a good idea.

When a person with an immunoglobulin-mediated allergy is exposed to an allergen, such as pollen, pet dander, or certain foods, their immune system reacts by releasing histamine and other chemicals, leading to an immediate reaction like itching and swelling.

Non-immunoglobulin mediated allergies, on the other hand, do not involve the production of IgE antibodies. Rather, they can come from different immune pathways—like food intolerances or reactions involving T cells. Which are the steps through which the immune system detects and eliminates foreign substances in the body.

Allergists rely on three types of tests to check for immunoglobulin-mediated allergies (and non-immunoglobulin mediated allergies): blood tests, skin prick tests, and patch tests. Here is what you need to know about each type:

IgE Blood Tests

Most of the time, the allergist will order a total IgE level as well as labs looking into IgE antibodies to specific substances. Together you’ll decide what makes sense to test for (from cats to walnuts to mold to grass).

One advantage to blood tests over skin prick tests is you don’t have to go off antihistamines or steroid medications for several days in advance of the test for the results to be accurate. For some allergens, allergists can order “component testing,” a newer blood test that looks for specific proteins that may particularly predict a risk of anaphylaxis. But component tests aren’t available yet for every food. A downside to blood testing is you have to wait for results. Also worth noting: Not every allergist does blood testing; some prefer to start with skin prick tests.

Skin Prick Tests

In skin prick tests, the provider pricks your skin with a sample of different allergens. Then they wait for a period of time (typically 15-20 minutes) to see whether you react in the form of hives, which indicates a true IgE-mediated allergy.

To conduct the test, the doctor or nurse will prick your upper arm or back with allergen extracts (cat, cashew, dust mites, etc), as well as two controls: histamine and saline. Histamine is something all of us react to. Saline is something your skin shouldn’t react to. If it does, it suggests you have very reactive skin and the test might not yield useful results.

After a period of time, usually 15-30 minutes, your provider checks to see if any of the substances gave you wheals—a raised hive.

After the waiting period your provider will measure any hives that may have formed. If any are bigger than the wheel to the histamine control, this means you are allergic to this substance.

Before you go in for skin prick tests, you need to stop certain medications. Your doctor’s office will instruct you to go off all prescription and over-the-counter antihistamines and some other drugs for a period of time (usually 5-10 days, depending on the doctor’s preference).

If it turns out that your IgE allergy skin prick and blood testing are all negative, that may suggest you have intrinsic eczema, which is not linked to IgE-mediated allergies. Research published in the Journal of Allergy and Clinical Immunology suggests there may be genetic factors involved in intrinsic eczema.

Patch Tests

There’s a third type of test that doctors use to test for allergies and sensitivities: patch testing. These tests, which can be done by a dermatologist or an allergist, check for non-IgE mediated allergic skin reactions (a.k.a. contact dermatitis)—a type of delayed allergic reaction that happens three to five days after your skin is exposed to an allergen. “Usually, these reactions are more localized and more common in adults,” Dr. Parikh says.

Here’s how these tests work: The doctor applies the suspected skin allergen to the skin under an occlusive film. It is left on the skin for several days. When the film is removed, your allergist or derm will check for a red or inflamed skin reaction. “One of the most common causes of contact dermatitis is nickel allergy, which presents as red, raised and inflamed skin where nickel came into contact with the skin,” says Dr. Smith. “I often see this from wristwatch bands and costume jewelry.”

Other common culprits include preservatives and fragrance in personal care and household products, rubber compounds, and lanolin—a natural wax from sheep’s wool—used in some moisturizers.

If you’re positive on a patch test, your doctor will likely advise you to remove any jewelry, clothing, or personal care products that contain that substance.

Note on Sensitivities

Sensitivity vs. Allergy

A sensitivity is something that makes your skin act up when it comes into contact with it, but it’s not an actual allergy. “An allergy is a true immune reaction against a particular substance,” says Dr. Parikh. “Your body forms IgE antibodies that trigger your mast cells to cause a cascade in your immune system that causes allergy symptoms. This can be serious or life threatening, depending on the allergen.” A sensitivity doesn’t involve your immune system and is not usually dangerous.

A sensitivity can make you super uncomfortable though and play a role in eczema flares. So, it’s worth noting if your flares come after you put a certain lotion on or switch your laundry detergent, and report back to your doctor. Sensitivities can be checked via patch tests—if you find a culprit, you will just need to make sure that troublemaker isn’t touching your skin.

Note on Intolerances

Food Allergy vs. Food Intolerance

If a certain food leaves you with bloating, gas, or irritated, itchy skin but you are negative on allergy tests, you may have a food intolerance. A food intolerance reaction occurs in the digestive system, not the immune system, per the American Academy of Allergy, Asthma & Immunology (AAAAI). But since it may cause inflammation, it can still play a role in eczema. Some of the same foods that cause food allergies are common culprits with intolerances and can flare up eczema. The list includes soy, eggs, peanuts, tree nuts, shellfish, and wheat).

But it’s not just about removing foods from your diet. There are also foods some experts believe can be added, for an eczema-friendly diet. Fatty fish like salmon, which has omega-3 fatty acids, is anti-inflammatory. The antioxidant quercetin, found in apples, berries, broccoli, red grapes, onions, cherries, and green tea, may help eczema, according to test tube research published in Pediatric Allergy, Immunology, and Pulmonology. And a healthy, Mediterranean-style eating plan, which favors fresh fish, fruits and vegetables, herbs, and whole grains, has been shown to have anti-inflammatory properties as well.

Treatment

Treating Allergies for a Clear Future

Depending on your exact allergy, the best treatments might include prescription or OTC antihistamines; steroid or antihistamine nasal sprays; and other systemic medications. If your testing uncovers a true food allergy, you will need to remove that food from your diet and be careful about avoiding cross contamination. Your allergist will prescribe an epinephrine auto injector, such as EpiPen or AuviQ, and share specific instructions about when to use the device and get to an emergency room.

Finally, preventive measures may make a big difference, too. Some allergists, like Dr. Smith, use allergy shots with some people to get allergic eczema under control. They require a time investment: You’d need to go to your allergist to be injected with your allergens once or twice a week for a period of six months or so, and then you’d enter a maintenance period where you’d need injections less frequently. “Allergy immunotherapy is a way to desensitize the body to your allergens gradually,” Dr. Smith says, “which not only improves your symptoms but can help clear your eczema.”