How Are Allergies and Atopic Dermatitis Related?

Allergies and atopic dermatitis (eczema) often go hand in hand. But experts do not think one causes the other. Instead, shared risk factors and an increased exposure to certain allergens may lead to both.^1,2

What are allergies?

Allergies come in several forms. They are often triggered by an allergen. Some allergens are foods. Common food allergens are peanuts (or other nuts), soy, and milk.³

Allergens also can occur in the environment, including pollen, dust, mold, and grass.
Allergies to things in the environment lead to seasonal hay fever. Another term for this is allergic rhinitis. Symptoms of hay fever include runny nose, watery eyes, sneezing, and coughing.^1-4

Certain ingredients in soaps, dyes, jewelry, and fabrics can cause allergic contact reactions. Examples include chemicals added to household cleaners and certain metals, like nickel, used to make jewelry.^1-4

The immune system and allergic reactions

An allergic reaction starts in the immune system. It is a complex process. The process involves proteins in the immune system called antibodies. The most common antibody involved is called immunoglobulin E (IgE). Other proteins called cytokines are involved in the allergic response too. Cytokines play a role in inflammation.^1-3

Symptoms of allergic reactions can range from watery eyes to very itchy, full-body hives (urticaria). Severe allergic reactions that impact breathing and other organs can be life-threatening. This type of reaction is called anaphylaxis.³

Is eczema the same as allergies?

While eczema can cause itchy, red skin like an allergic reaction, it is not the same. One main feature of eczema is dry, weak skin. Another aspect of eczema is an overactive immune system response. Although the immune system is active in eczema flare-ups, a different set of inflammatory proteins is at play than in allergies.^1,3,5

People with allergies often have higher levels of immune system cells called eosinophils. These cells are also involved in other health issues, like eosinophilic esophagitis (EoE). EoE is inflammation of the esophagus, the tube that connects the mouth to the stomach.^1,6

It is possible for people with eczema to have higher levels of IgE too. However, this is not always related to their skin response. IgE levels can also vary greatly from person to person and are not related to how severe symptoms are.^1,5

Eczema leading to allergies

Some experts believe that the weakened skin barrier in eczema makes it easier for allergens to enter the body. If a person has an irregular immune system response too, they may have a higher risk of developing an allergy. This process is called sensitization.^1,4,5

On the other hand, some allergens may act as triggers for eczema symptoms. These flare-ups can be caused by food, chemical, or environmental allergens. Allergens affect different people differently. For example, babies are commonly more sensitive to food allergens. Kids over 5 years old and adults are more likely to be sensitive to allergens in the environment.^1,4,7

Identifying and avoiding whatever triggers impact you can help manage your eczema symptoms.^1,4,7

What is the atopic march?

Eczema, allergies, and asthma are all called atopic conditions. The development of all 3 over a lifetime is called the "atopic march." These issues can arise in any order or at the same time. However, it is common for babies to develop eczema first and then allergies and asthma. As many as 80 percent of kids with eczema will have the atopic march.^1,7

Diagnosing allergies

It is possible to be sensitized to an allergen without being allergic. It is also possible to have skin reactions that look like allergic reactions but are just irritation. A true allergy causes both symptoms and higher levels of IgE related to that specific allergen. IgE can be measured through blood tests. You and your doctor can track your clinical symptoms.¹

Keeping a diary of reactions and potential allergens will help with diagnosis. Skin prick tests may also be useful. These tests involve exposing the skin to allergens and watching for a response. There is also a blood test available for allergies. But not all allergy tests are perfect. Some can lead to false positive results.^1,7-9

For this reason, experts do not recommend allergy testing for all people with eczema. Testing may help identify a trigger when symptoms are present. They may also be valuable for people with more severe forms of eczema.^1,7-9

Treating allergies

The best way to manage allergies varies. Some people may have mild symptoms during pollen season that respond to over-the-counter allergy drugs. Others may have severe reactions that require treatment by an allergist. An allergist is a doctor who specializes in allergies and the immune system.^3,7,8

Some people may have such severe allergies that they need to carry an EpiPen with them. These are pen-like injectors that contain a drug called epinephrine to treat life-threatening anaphylaxis reactions. Other drugs or allergy shots may be helpful based on the specific allergen and reaction.^3,7,8

For people with eczema, one of the best ways to prevent allergies from developing is to keep the skin barrier strong. Moisturizing with over-the-counter lotions or prescribed treatment creams can prevent dryness and cracking. This helps stop allergens from entering the body easily. Moisturizing is especially important for babies and young children before allergies have the chance to develop.^4,7,8