Articles (EN)

Allergy to complementary foods: how to introduce new foods safely

2026-05-26 12:00 Complementary Feeding
In short: Current evidence shows that early (within the age norms) introduction of allergenic foods reduces, rather than increases, the risk of food allergies. The main rule is one product at a time with an interval of 3-5 days and in the morning. Do not postpone allergens "for later" without medical indications.

Why allergies occur during complementary foods

When a child first encounters a foreign protein — whether it's egg white, cow's milk casein, or wheat gluten — the immune system "decides" how to treat it. Most children have a calm reaction: tolerance is formed. In some cases, the immune system mistakenly attacks a harmless protein, causing allergies.
The risk is increased with:
  • Atopic dermatitis in a child (especially moderate and severe).
  • Allergy to other foods, already identified earlier.
  • Hereditary predisposition (allergies in parents or siblings).
Important: heredity increases the risk, but does not determine the outcome. And, crucially, the storage of allergens does NOT reduce this risk – the evidence suggests otherwise.

The main food allergens in children

The WHO and most national organizations identify 8 key allergens, which account for more than 90% of all food allergic reactions:
  • Cow's milk
  • Chicken egg
  • Wheat (gluten)
  • Soybeans
  • Peanuts
  • Tree nuts (walnuts, almonds, cashews, etc.)
  • Fish
  • Seafood (crustaceans, molluscs)
They should be introduced not less often, but within the age norms. Current guidelines (AAP 2019, LEAP study) make it clear that for most children — including those with mild atopic dermatitis — early administration of peanuts reduces the risk of allergies. There is similar data on eggs.

How to introduce allergenic foods: a step-by-step approach

  1. Choose the morning. Give the allergen in the first half of the day so that you can observe the reaction for several hours.
  2. Start small. Literally 1/4 teaspoon of a new product. If there is no reaction, increase the portion after 1-2 days.
  3. One product at a time. Do not mix two unfamiliar ingredients. If a reaction occurs, you should know the cause.
  4. Soak for 3-5 days. During this time, delayed allergy (IgE-mediated and non-IgE-mediated) usually appears.
  5. Fix. Write down what was injected and what the reaction was. This will help the pediatrician.

How to distinguish an allergy from a normal reaction

After the introduction of a new product, there may be changes in the stool, slight redness around the mouth or slight bloating. This is not necessarily an allergy - this is how the digestive system adapts to the new. A true allergic reaction manifests itself in a different way:
  • Skin symptoms: hives (red itchy blisters), swelling of the lips, face, rash behind the ears or in skin folds.
  • Gastrointestinal symptoms: vomiting, diarrhea, blood in the stool (typical for CMPA - allergy to cow's milk protein).
  • Respiratory symptoms: runny nose, cough, wheezing, difficulty breathing.
  • Anaphylaxis: a combination of several systems – skin + respiration + blood circulation. Requires immediate medical attention.
Important: If the child has difficulty breathing, his lips turn blue, he has lost consciousness or his blood pressure has dropped sharply, call an ambulance immediately. This is anaphylaxis, it is life-threatening.

Children at risk: do we need special care?

In case of severe atopic dermatitis or already identified allergies, yes, the allergen regimen is discussed with an allergist or pediatrician. In some cases, skin tests or controlled administration of the product in a doctor's office are recommended. You should not limit the diet "just in case" on your own: this will not reduce the risk of allergies, but it can create a nutrient deficiency.
If you are just starting complementary foods and want to figure out the order of products, read the article "How to start complementary foods: first products by month". About gluten in complementary foods - a separate material with an analysis of myths.

What to do if a reaction has already appeared

  1. Stop giving the suspected product.
  2. In case of a slight rash or redness, observe and consult a pediatrician as soon as possible.
  3. In case of swelling of the face, difficulty breathing, loss of consciousness, call an ambulance immediately.
  4. Record: what was given, when, how much and what was the reaction - the pediatrician will ask about it.
  5. Do not reintroduce this product before consulting your doctor.

When to see a doctor

  • After the introduction of the product, a rash, swelling or any signs of allergy appear - contact your pediatrician.
  • You suspect an allergy to cow's milk protein (CMPA) – blood in the stool, constant anxiety, eczema, poor weight gain.
  • The child has severe atopic dermatitis - before the introduction of allergens, a consultation is needed.
  • The child refuses complementary foods and reacts to food with strong anxiety.
  • After the start of complementary foods, constipation or diarrhea appeared.
  • There are alarming signs in the development along with food reactions.

Frequently Asked Questions

If the mother ate the product during pregnancy, is the child already "familiar" with it?

In part, yes: antigens of some foods penetrate the placenta and into breast milk. But this does not guarantee tolerance and does not negate the need for a phased introduction. It is still important to start complementary foods at 6 months with the gradual introduction of allergens.

Is it necessary to do tests before introducing allergenic products?

For healthy children without risk factors, no. Routine testing prior to first exposure to the product is not recommended. If there is a risk (severe dermatitis, already identified allergies) – only on the prescription of an allergist.

Conclusion

Fear of allergies should not turn the introduction of complementary foods into stress. A systematic approach — one product, 3-5 days, morning — makes the process safe and manageable. There is no point in postponing allergens: modern science says that timely acquaintance with them is more likely to protect than harm. If you have any doubts, a pediatrician and an allergist will help you build an individual plan. Do not forget about meat in complementary foods as an important source of iron and zinc from 6-7 months.

Bibliography

  1. Du Toit G, et al. Randomized Trial of Peanut Consumption in Infants at Risk for Peanut Allergy (LEAP). N Engl J Med. 2015; 372:803–813.
  2. AAP. Preventing Allergies — New Guidance on Introducing Allergenic Foods. Pediatrics. 2019; 143(4):e20190281.
  3. ESPGHAN. Complementary Feeding: A Position Paper. J Pediatr Gastroenterol Nutr. 2017; 64(1):119–132.
  4. Perkin MR, et al. Randomized Trial of Introduction of Allergenic Foods in Breast-Fed Infants (EAT Study). N Engl J Med. 2016; 374:1733–1743.
  5. WHO. Strategies to Prevent Obesity and Other Chronic Diseases — The WHO European Childhood Obesity Surveillance Initiative. WHO, 2009.
  6. National program for optimizing the feeding of children in the first year of life in the Russian Federation. Union of Pediatricians of Russia, 2019.
This material is for informational purposes only and does not constitute medical advice and is not a substitute for medical advice. If there are any signs of an allergic reaction in a child, consult a pediatrician or allergist. In case of anaphylaxis, call an ambulance immediately.