Risk Factors for Food Allergy

Several factors can increase a person’s risk for food allergies. These include

• Eczema
• Genes
• Changes to the microbiome (the microscopic organisms that live in and on our bodies)

Eczema

The skin disease called eczema is the biggest risk factor for developing food allergies. Children with moderate to severe eczema have a greater risk for food allergies than children with mild or no eczema. This finding has led to the idea that children with eczema may have their first contact with a food allergen by absorption through their abnormal skin rather than by eating. Scientists think the immune system may perceive food allergens absorbed by the skin as invaders, and this can lead to food allergy. Both eczema and food allergy have become much more common over the past several decades, supporting the idea that the two are related.

Genes

Genetic factors also influence the development of food allergy. NIAID-funded researchers studied children who had avoided eating peanut until age 5 and found that kids who had a gene called MALT1 were much more likely to develop peanut allergy than kids who did not. A group of NIAID scientists are now studying the genetic basis of food allergy in children and adults with the condition. The study also includes people who have a genetic or birth disorder associated with food allergy or a related allergic disease, such as eczema.

Changes to the Microbiome

Many researchers think environmental changes during the past few decades may be altering our miocrobiome—that is, the community of bacteria, fungi and other microscopic organisms that naturally live in and on our bodies. These environmental changes include overuse of antibiotics and hand sanitizers, a shift from rural to urban living, sterile indoor environments, and an increase in births by caesarian section (C-section). The impact of these changes on our microbiome may be affecting our immune health, including making food allergies more common.

Some research suggests that babies born by C-section rather than through the vaginal canal have a higher risk for developing food allergies and some other diseases. Scientists speculate that this may be because these babies do not get exposed to their mothers’ vaginal microbiome, which in turn affects the development of the babies' microbiome. The gut microbiome of children born by C-section is less diverse than the gut microbiome of children born vaginally. Perhaps as a result, the immune systems of infants and toddlers who were born by C-section are less capable of developing and maintaining tolerance to allergens than the immune systems of infants and toddlers who were born vaginally.

The NIAID-funded Immune Tolerance Network is doing a small clinical trial to find out whether exposing babies born by C-section to their mother’s vaginal microbiome right after birth lowers the risk that the child will develop food allergies. Study staff wipe half of the babies born by C-section with gauze soaked in the mother’s vaginal fluid and half with sterile gauze. A year later, the researchers test the children for sensitivity to food allergens. Study results are expected in 2025.

Further Research

Researchers funded by NIAID are doing a study called SUNBEAM to discover additional traits of children who have a greater risk for food allergy and eczema than other children. The scientists also aim to pinpoint more environmental exposures and biological pathways that lead to food allergy and eczema. The study includes 2,500 families with children ages 0 to 3 years.

The SUNBEAM scientists are analyzing a huge amount of data gathered from the families through

• biological samples, like blood and urine
• home environment samples, like dust and water
• responses to surveys

The surveys ask questions about the families’ health history, allergies, diet, infant feeding practices, home environment, mental health, and characteristics like race, ethnicity, and language.