Genes aren’t the only factor at play in determining which children will develop a food allergy, a new evidence review says.

Antibiotic use, the presence of other immune system diseases, and delayed introduction of allergenic foods all also can play a role in the start of childhood food allergies, researchers reported Feb. 9 in JAMA Pediatrics.

“Our study highlights that genetics alone cannot fully explain food allergy trends, pointing to interactions – or a ‘perfect storm’ – between genes, skin health, the microbiome and environmental exposures,” senior researcher Dr. Derek Chu, an assistant professor at McMaster University in Canada, said in a news release.

For the study, researchers analyzed data pooled from 190 studies involving 2.8 million participants across 40 countries.

Results showed that about 5% of children develop a food allergy by age 6.

The team then systematically examined more than 340 different factors that can influence allergy.

Some early-life factors that increase risk of food allergies include:

• Eczema within the first year of life, which triples to quadruples a child’s risk.

• Nasal allergies, which triple risk, or wheeze, which doubles risk.

• Having allergic parents or siblings, with the risk more than doubled if both parents had allergies.

• Waiting too long to introduce foods like peanut, nuts, eggs or other common allergens, with babies more than twice as likely to have peanut allergy if they try them after 1 year old.

• Antibiotic use within the first month of life, which quadruples risk.

Antibiotics taken while pregnant or during a baby’s first year also increased food allergy risk, but only by 32% to 39%.

On the other hand, the review ruled out many factors suspected of playing a part in food allergies, including low birth weight, post-term birth, lack of breastfeeding as well as a mother’s diet and stress during pregnancy.

These results could help identify babies at risk of food allergies and potentially ward them off through early prevention, researchers said.

“This study has broadened our understanding of food allergies,” Chu said. 

“Future studies should measure and adjust for the same key factors, include more diverse populations and use food challenge testing more often,” he said. 

"New randomized clinical trials and updated guidelines are urgently needed to move our findings into action,” Chu added.