What You Need to Know About Peanut Allergies

Mmmm peanut butter. Peanut butter is a staple of American diets. The United States grows almost all of the world’s peanuts, and during World War II this cheap, healthy food became the go-to way to get protein and calories. 

And it stuck because peanut butter is delicious. 

Unless you come from a peanut allergy-home, your baby is going to eat peanut butter sooner or later. And their first bites of peanut butter will most likely come at home. 

Here are some things you should know about peanut allergies and babies before you introduce your baby to peanut butter.


How Common Are Peanut Allergies?

Peanut allergies are very common. About 5% of 1 year olds in 2017, or 1 in 20 1 year olds, developed a peanut allergy. This may not seem like a lot, but considering 4 million babies are born in the U.S. every year, 5% is quite a large number.

 

chart showing 1 in 20 babies develops a peanut allergy

1 in 20 1 year olds developed a peanut allergy in 2017

 

Between 2001 and 2017, the rate went from an estimated 1.7% to 5.2%. This increase in peanut allergies is new. As recently as 2001, only 1.7% of 1 year olds developed a peanut allergy. 

Today, about 2.2% of children & teens in the U.S. have a peanut allergy. 

You likely already know several people with a peanut allergy. As your baby grows up, you will know many more. You’ll also likely meet babies with allergies to dairy, eggs, wheat, tree nuts, soy or sesame. Together, those food allergies affect nearly 10% of infants.   


Risk Factors For Developing a Peanut Allergy

Peanut allergies seem to strike at random. Even among twins, one sibling will develop a peanut allergy when another one doesn’t. 

The real predictors of peanut allergy are:

The most studied risk for developing a peanut allergy is eczema. The earlier a baby develops eczema, and the more severe it is, the more likely he will develop food allergies. 

graph showing babies with severe eczema developed food allergies at a higher rate

One study looked at babies with no, mild, medium, and severe eczema and tracked them to see who developed food allergies. The graph above shows the results of that study.

  • Babies who developed eczema by 3 months old, and needed prescription strength medicines, had a 50% rate of food allergy. 
  • Babies who developed eczema later, closer to 1 year old, and needed only emollients, had only a 5% rate of food allergy.

The current guidelines from the American Academy of Pediatrics decide how a baby should start eating peanuts based on the severity of their eczema. 

 

Chart showing when babies should start eating peanuts based on their level of eczema

4- 6 month old babies that have:

  • No eczema or food allergies should start eating peanut-containing foods 3 times a week at home as soon as they can eat solid foods. 
  • Mild eczema that responds to emollients or over-the-counter medicines should start eating peanut-containing foods 3 times a week at home starting at 6 months old. 
  • Severe eczema that requires prescription drugs, egg allergy, or both should see a doctor to get tested for peanut sensitization
    • Babies who are not sensitized should begin eating peanuts 3 times a week starting between 4-6 months old. 
    • Babies who are sensitized, but pass a food challenge, should begin eating peanuts 3 times a week starting between 4-6 months old.

Only babies with a developed peanut allergy (less than 0.5% of babies) should avoid peanut.  

 

What is Sensitization to Peanuts?

A sensitization to peanuts means your baby’s body has created IgE antibodies specific to peanut protein. Sensitization is not an allergy. An allergy is when the body attacks peanut protein. Sensitization means your baby’s body has flagged peanut, but still may not decide to attack.

Many babies can be sensitized to peanuts but not have a reaction (an allergy) when they eat peanut. 

Knowing the difference between sensitization and an allergy is incredibly important. The LEAP study showed that when babies who were sensitized to peanut started eating peanut early and often, 90% did NOT develop a peanut allergy. However, if they avoided peanut, 35% developed a peanut allergy. 

 

Can You Test for a Peanut Allergy?

The only real peanut allergy test is a reaction to peanut when eaten, known as an oral food challenge. 

A doctor can test for an IgE sensitization to peanut by checking for IgE antibodies specific to peanut using a blood test or a skin prick test. But as we mentioned above, proof of sensitization to peanut does not confirm your baby has an allergy.

 

Peanut Allergy Blood Test

In a blood test, doctors take a small sample of your baby’s blood and check for IgE antibodies to peanut. If your baby is sensitized to peanut already, those antibodies will be in the blood sample. 

The number of antibodies in a blood sample reflects the likelihood or probability of a food allergy, not the severity of a food allergy. The higher the count of antibodies, the more likely a baby is to develop an allergy.

 

Peanut Allergy Skin Prick Test (SPT)

In a skin prick test, doctors place a tiny droplet of water containing an even tinier amount of peanut on your baby’s skin, and then prick the skin just enough to let that droplet in. After 20 minutes, the doctor checks your baby’s skin for a reaction — like redness or swelling — and measures the size of that reaction. The size of the reaction tells you the probability of a food allergy.

Here is a longer overview of food allergy testing.


Beware Online Food Tests: Online food sensitivity tests are not accurate and only test for a food sensitivity/food intolerance, not IgE sensitization or an allergy.

Read more about the difference between food sensitivities vs. food allergies


Final Thoughts

At the end of the day, peanut allergies are incredibly common, and there’s no one way to tell whether or not your baby will develop an allergy. The best thing you can do is understand your baby’s level of risk and introduce peanuts  following the American Academy of Pediatrics and your doctor’s recommendations.