Food allergy affects approximately 2% to 10% of the population. Studies suggest that early introduction of common allergenic solids such as eggs and peanuts, especially in high risk infants, may have a role in preventing food allergy. For infants at high risk for food allergy, it is recommended that common allergenic foods should be introduced around 6 months of age, but not before 4 months. 

The most common food allergens in children are cow’s milk, egg, peanut, tree nuts, fish, shellfish, wheat and soy. 

Who is at high risk for food allergies?

Older guidelines defined infants at risk for having food allergies as those with a first degree relative with an allergic condition. A recent study found that infants who have severe eczema, egg allergy or both are at higher risk of developing peanut allergy.

Currently, it is believed that infants at high risk for food allergies include those with a personal history of atopy (such as eczema), or have a first degree relative with atopy. Atopy is a genetic predisposition to develop an allergic reaction such as allergic rhinitis, asthma and eczema. 

Which food allergens will early introduction show reduction of risk?

The best evidence is for early introduction of peanuts in high risk infants.  Babies are higher risk of peanut allergy who are exposed to peanut earlier may have a reduced risk of peanut allergy at 5 years of age

There are studies suggesting that early introduction of eggs may lead to less likelihood of developing egg allergy in high risk infant as well. 

When should you see an allergist?

Infants and children should see an allergist in the following scenarios:

  • History of immediate IgE mediated symptoms (rash, swelling, vomiting, diarrhea, shortness of breath, low blood pressure) after food ingestion. 
  • History of gastrointestinal symptoms (projectile vomiting, severe diarrhea, with or without paleness, lethargy)
  • Infants with chronic diarrhea, failure to thrive, or weight loss should be referred to an allergist in addition to gastroenterology and general pediatrics. These patients may have a non-IgE mediated food allergy such as food protein-induced enterocolitis syndrome (FPIES) or allergic protocolitis. 

Infants with a personal history of egg allergy, moderate-severe atopic dermatitis or both should be introduced to allergenic foods at 6 months, but not before 4 months. American guidelines recommend that these infants should undergo skin prick or specific IgE testing for peanut allergy prior to introduction of peanut. In Canada, this is assessed on an individual basis depending on the patient’s atopic comorbidities and parental anxiety.

This post was co-authored by Ling Ling, MD, FRCPC, BSc,  Stephanie Liu, MD, MSc, CCFP, BHSc and Erin Manchuk, BScPharm, BCGP.

Dr Ling Ling is an allergist and immunologist in the division of Pulmonary Medicine, University of Alberta. She is a graduate of the University of Alberta Medical School and Internal Medicine training program. She completed her Clinical Immunology and Allergy fellowship at Mcmaster University. She currently sees adult and pediatric allergy patients at the University of Alberta and in private practice.