What are the Risk Factors for Food Allergies?
When I was pregnant with my first son (who has multiple food allergies) I read a book called An Epidemic of Absence and promptly became petrified of food allergies developing in my child. Using this book and other research as my guide, I made sure to have a clean, but not have overly clean household, and even expose him to germs. But I never looked into the research to understand real risk factors associated with food allergies. And while there was nothing particularly wrong with the insights I gained from this book, it turns out cleanliness likely had no real impact on our risk of allergens. So for your sake, here are the most understood risk factors associated with food allergies in children:
Family history of Food Allergies:
There is at least some genetic component to food allergies. A baby has a 7x increased risk of developing a peanut allergy if a parent or sibling has a peanut allergy. Twins are at a higher risk of both having allergies.
Why genetics predisposes you is not totally clear, though it may have to do with some epigenetics, or gut microflora that are passed from mother to child.
Having Eczema, and the Severity of the Eczema
Babies with eczema have a compromised skin barrier that is the result of atopic dermatitis (AD) and transepidermal water loss (TEWL). This condition is noted as perhaps the single biggest predictor of food allergies. There is also a noted relationship between the severity of the AD and food sensitization. That is why the LEAP study used babies with eczema as their definition of a high risk group, and why the current FDA language advises you to talk to your doctor before introducing allergens if your baby has eczema.
Why is a skin condition linked to food allergies? The short answer is that when the skin barrier is compromised, food dust breaks through the skin. This causes sensitization. Then later, when the baby eats the same allergen, the body goes into immune response. We’ll make a full blog post in the coming weeks on the “dual-allergen exposure hypothesis” sometimes also called the “atopic march.”
Being a Boy
For babies, male children are 5x more likely to have peanut and tree nut allergies. BUT, they are also more likely to outgrow them. By adulthood the rate of allergies is close to even between males and females. This difference has also been noted for asthma. Differences by sex imply a role for endocrine influences.
Living in a City
Research by the SOAAR group found that 9.8 percent of children living in urban centers have food allergies, compared to 6.2 percent in rural communities. That is nearly a 3.5 percent difference. Increasing population density corresponded with increasing food allergies and asthma, with odds in urban versus rural areas highest (odds ratio 1.7), followed by metropolitan versus rural areas (odds ratio = 1.4). This difference remained after adjusting for race/ethnicity, gender, age, household income, and latitude. Shellfish allergies are three times as common in city kids, and peanut allergies were twice as common.
This research shows that the environment plays a role in a child’s risk of developing food allergies. But it does not explain why.
One study showed that non-Hispanic black children are three times more likely to have IgE sensitization to certain foods as compared to white children. For example, the prevalence of likely food allergy to shrimp in non-Hispanic black patients was 2.3% compared with 0.3% in non-Hispanic white patients. Another study showed that black children were more likely to be sensitized to multiple foods compared with white children. The racial division could be genetics, or it could have to do with our the geographical division by race in America.
Risk Factors Played Out In Real Life
Turns out, my male child, who was born and raised in a city, and had eczema had a trifecta of food allergy risks. If we had known the real risk factors early on, we would have been much more proactive about speaking to our pediatrician, treating his eczema, and (if the data had been out) introducing allergens early.
The more I continue to explore our understanding of food allergies, the more obvious it becomes that the onus is so often on the parent to find out this information.