If you have a high-risk baby, your pediatrician or allergist might run a blood test to measure peanut-specific antibodies. If the test is negative, you can be reassured that a peanut allergy is unlikely and go ahead and introduce it. If it’s positive, you should see an allergist for more testing, Dr. Fleischer said.
An allergist might do a skin prick test, which involves placing a tiny amount of a food protein under the skin, and watching for a reaction in the form of a raised, puffy “wheal.” A very big wheal means that your child is more likely to have an allergic reaction, but it’s also not a perfect test. The only way to truly diagnose food allergy is to see what happens when your baby eats the food, and more and more allergists are doing “food challenges” with babies in their offices, where they offer small amounts of the food and carefully monitor for signs of a reaction, with the capability to treat the child if necessary.
As an example, Dr. Fleischer said he once saw a very large wheal after a peanut skin test on an 8-month-old patient with severe eczema. The wheal was big enough that many allergists might have simply diagnosed it as a peanut allergy. But Dr. Fleischer gave the baby a food challenge with a small amount of peanut, and he didn’t react. He told the parents to continue regularly feeding him peanuts at home, and the child, who was 3 at his last appointment, can now completely tolerate peanuts. Dr. Fleischer thinks it’s likely this child would have developed an allergy without this exposure, given his eczema and reactive skin test.
Introduce peanuts early to prevent allergy, especially if your baby is high risk.
Government guidelines recommend that if your baby is high-risk (if they have severe eczema or an egg allergy), you should introduce peanut products as early as 4 to 6 months. If your baby has an intermediate risk (defined as mild to moderate eczema) the guidelines recommend feeding them peanut products around 6 months. If your baby is low-risk and doesn’t have eczema, you can take a more relaxed approach, introducing peanut products along with other solid foods when you prefer.
The recommendation to introduce peanut products to high-risk babies early was based off one study (the LEAP study), and how exactly to translate those findings is somewhat controversial. Some experts, Dr. Fleischer included, argue that parents shouldn’t stress about introducing peanuts and other allergens so early, noting that some babies won’t be developmentally ready to eat solids at that age. The important thing is to make peanuts and other allergens a regular part of your baby’s diet at least within the first year, Dr. Fleischer said.
Start by introducing a few fruit and vegetable purees, and once your baby has the hang of those, you can try some peanut products, said Dr. Carina Venter, Ph.D., R.D., a registered dietitian specializing in food allergies and an associate professor of pediatrics at University of Colorado Denver School of Medicine. She helped write the government guidelines, including practical and safe recipes for feeding peanuts to babies, since whole or partial nuts are a choking hazard and shouldn’t be offered to kids under age 5. For example, you can mix 2 teaspoons of smooth peanut butter into 2 to 3 teaspoons of hot water (letting it cool before feeding it); or into 2 to 3 tablespoons of fruit or vegetable puree. Start with a small amount of this mixture on the tip of a spoon, and then wait 10 minutes for signs of a reaction. If that’s tolerated, you can offer the rest of the serving.
NIAID guidelines recommend feeding 2 grams of peanut protein (in the form of 2 teaspoons of peanut butter or peanut flour, or 21 pieces of Bamba peanut puffs, for example) about three times per week, as was used in the LEAP study. But Dr. Venter said the most important thing is to keep peanuts as a regular part of the diet. “We don’t want to be anxious about dosing,” she said. “Babies get sick, they don’t want to eat, some days they want to eat lots more, some days they only eat a little bit.” And you want to enjoy feeding your baby, not stress about it, she added.