The link between atopic dermatitis and food allergies

Atopic dermatitis, also referred to as AD or eczema, is a chronic skin condition characterized by red or discolored, irritated, and itchy patches of skin. While there is a known correlation between atopic dermatitis and food allergies, it's still unclear whether food allergies worsen atopic dermatitis symptoms. Several decades of studies have shown that food allergies may exacerbate AD symptoms in some patients, though it does not appear to be common. When it does occur, food allergies most often affect young children with moderate to severe AD. The phenomenon of food allergies worsening AD is rare in older children and adults. 

The atopic dermatitis and food allergy link 

Researchers affiliated with Oregon Health and Science University in Portland and several other hospitals spent five years studying infants and toddlers with atopic dermatitis. They found that participants with more severe atopic dermatitis seemed to be at a higher risk for developing food allergies than those with milder symptoms. The findings were published in the journal Pediatrics in 2015. 

Understanding the connection 

Scientists speculate that there are several possibilities as to why this connection exists.

Atopic dermatitis usually occurs in people who have a vulnerability in their skin's outer layer. This makes the skin susceptible to irritants and allergens, including food. These allergens can easily penetrate the skin barrier and cause inflammation, itching, and other symptoms. 

It's also speculated that many food sensitivities can cause positive skin or blood allergy test results, though this kind of food sensitivity may not be indicative of a full-blown allergy. Nonetheless, because of a positive allergy test result, the person may avoid the food completely. As a result of this avoidance, they may not develop a normal tolerance for the food. In other words, avoiding certain foods may actually have the effect of causing more allergies. 

If your child has atopic dermatitis 

The National Institute of Allergy and Infectious Diseases recommends food allergy testing for all children under the age of 5 who are diagnosed with moderate to severe atopic dermatitis and have not had success in managing the condition, and those who have had symptoms of food allergies. Common signs of an allergic reaction to food include skin reactions, inflammation, breathing difficulty, or gastrointestinal upset that occurs after eating. 

If you suspect your child has a food allergy, speak with your child’s healthcare provider (HCP). Diagnosis of a food allergy typically involves a physical examination, medical history, and a number of tests that can help identify specific allergens.

Testing for food allergies

Testing for food allergies may include skin-prick tests and blood tests.

In a skin-prick test, an HCP uses a special needle to introduce potential allergens to the surface of the skin and observes for a reaction. Blood tests look for allergen-specific antibodies in the blood. 

Skin-prick tests and blood tests can identify sensitization to certain foods, but a diagnosis of a food allergy usually requires an oral challenge test as well. During an oral challenge test, the patient consumes small amounts of a potential food allergen as is then observed for allergic reactions. These tests need to be performed in a carefully controlled environment due to the risk of anaphylaxis, a life-threatening allergic reaction. 

While there is no cure for atopic dermatitis, there are treatment options available that can help manage symptoms. Knowing what substances trigger or exacerbate flare-ups—which for some people, may include food allergens—can help you manage the condition.