Early Introduction of Complementary Foods
How do you know an infant is ready for solid foods:
- Good head and neck control
- Ability to sit on their own with minimal support
- Opens mouth and leans forward when offered food
- Able to grasp larger objects and brings them up to the mouth
Some infants may show developmental signs of readiness before age 6 months, but introducing complementary foods before age 4 months – or waiting until after 6 months – is not recommended (1). Chapter 2 of the USDA Dietary Guidelines for Americans 2020-2025 encourage the introduction of potentially allergenic foods along with other complementary foods. In addition to peanuts, the Dietary Guidelines for Americans 2025 recommend eggs, cow milk products, tree nuts, wheat, crustacean shellfish, and soy be introduced when other complementary foods are introduced.
The American Academy of Pediatrics states that: “There is no evidence that delaying the introduction of allergenic foods, including peanuts, eggs, and fish, beyond 4 to 6 months prevents atopic disease.”
Which foods should my patient eat, and how much?
The American Academy of Pediatrics states that: “There is no evidence that delaying the introduction of allergenic foods, including peanuts, eggs, and fish, beyond 4 to 6 months prevents atopic disease.”

When counseling families on food introduction, it is important to discuss how to tell when an infant is ready for solid food and what foods are developmentally appropriate. If serving purees, families should aim for a smooth, even texture for the baby’s first few foods. First finger foods given to an infant should be very soft and easy to smash between the thumb and forefinger. For thicker foods, such as nut butters, it is best to thin them out with warm water or mix them into something smoother, such as applesauce. Some signs that a baby is ready to try solid foods are:
- Good head and neck control
- Ability to sit on their own with minimal support
- Opens mouth and leans forward when offered food
- Able to grasp larger objects and bring them up to the mouth
Some infants may show developmental signs of readiness before age 6 months, but introducing complementary foods before age 4 months — or waiting until after 6 months— is not recommended (1). Chapter 2 of the USDA Dietary Guidelines for Americans 2020-2025 encourage the introduction of potentially allergenic foods along with other complementary foods. In addition to peanuts, the Dietary Guidelines for Americans 2025 recommend eggs, cow milk products, tree nuts, wheat, crustacean shellfish, and soy be introduced when other complementary foods are introduced. Although only peanut has guideline-based recommendations for quantity and frequency (2 grams of peanut protein, 3x a week), there are currently no guideline recommendations for quantity or frequency of other allergenic foods. Looking at available studies, including the LEAP study (1), EAT study (2), and others, 2 grams of allergen protein twice a week may be a reasonable target. For foods like egg, dairy, wheat, and soy, more frequently may make sense, as these foods are ubiquitous in our diets. In the case of fish and shellfish, slightly less frequently (e.g., once a week) may equally be reasonable based on family and household consumption and accessibility.
One may determine the grams of protein by using the specification on the nutrition label of the grams of protein in a particular serving size of the food, and utilizing this measurement to calculate the goal dose of 2 grams. For the case of nut butters and sesame tahini, a little more than 2 teaspoons may be the target. In the case of egg, about 1/3 of a large egg may be the target. For fish and shellfish, in general, the serving size is about the size of the palm of a child’s hand; however, 2 grams is also the goal.
There are many factors to take into account when deciding what foods parents should introduce to their children, and when each food should be introduced. Because there are no official guidelines for most foods, it is important to utilize a shared decision-making process with the family and take into account preferences they may have. This allows for the personalized application of recommendations based on the most current and promising research. See Shared Decision Making for the Allergist for the full study (3).
Gut vs. Skin: The Dual-Exposure Hypothesis
An important aspect to consider when deciding what foods to introduce is to consider what foods the family eats regularly, as environmental exposures to allergenic foods may be a risk factor in developing allergies. It is also important to consider what foods fit with a family’s preference, taste, and culture.
Under the dual-exposure hypothesis, if a child avoids oral exposure of an allergenic food (e.g. peanuts), but experiences frequent environmental exposures through their skin, they may be more likely to develop a sensitivity or allergy to peanut. When a child is exposed to a food allergen via the skin (e.g. food touches the skin), the immune cells of the skin are more likely to cause sensitization to that food. This is especially true if the skin is inflamed or irritated, as is the case with eczema. However, when a child is exposed to a specific food via the oral route (e.g. food is consumed), the immune cells in the digestive system create a tolerance to that food. (4,5)
Dual Exposure Hypothesis

Under the dual-exposure hypothesis, if a child does not already have an allergy and is routinely exposed to the allergen (e.g. peanut) orally, through the gut this may lead to induction of tolerance to that allergen. T-regulatory cells within mesenteric lymph nodes may play a role (lack).
Nutrition Guidance for Families
References:
- Du Toit, G., Roberts, G., Sayre, P.H., Bahnson, H.T., Radulovic, S., Santos, A.F. et al. Randomized trial of peanut consumption in infants at risk for peanut allergy. N Engl J Med. 2015; 372: 803–813.
- Perkin, M.R., Logan, K., Tseng, A., Raji, B., Ayis, S., Peacock, J. et al. Randomized trial of introduction of allergenic foods in breast-fed infants. N Engl J Med. 2016; 374: 1733–1743
- Blaiss MS, Steven GC, Bender B, Bukstein DA, Meltzer EO, Winders T. Shared decision making for the allergist. Annals of Allergy, Asthma & Immunology. 2019 May 1;122(5):463-70.
- Du Toit G, Sampson HA, Plaut M, Burks AW, Akdis CA, Lack G. Food allergy: Update on prevention and tolerance. Journal of Allergy and Clinical Immunology. 2018 Jan 1;141(1):30-40.
- Lack G. Update on risk factors for food allergy. Journal of Allergy and Clinical Immunology. 2012 May 1;129(5):1187-97.
- U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th Edition. December 2020. Available at DietaryGuidelines.gov.
- Greer, F. R., Sicherer, S. H., Burks, A. W., COMMITTEE ON NUTRITION, & SECTION ON ALLERGY AND IMMUNOLOGY (2019). The Effects of Early Nutritional Interventions on the Development of Atopic Disease in Infants and Children: The Role of Maternal Dietary Restriction, Breastfeeding, Hydrolyzed Formulas, and Timing of Introduction of Allergenic Complementary Foods. Pediatrics, 143(4), e20190281. https://doi.org/10.1542/peds.2019-0281
- National Institute for Allergy and Infectious Disease. Addendum Guidelines for the Prevention of Peanut Allergy in the United States.; 2017. doi:10.1097/01.JAA.0000512231.15808.66