An allergic reaction in babies starts when the immune system overreacts against a certain component in food or so-called allergens.
The FDA created a list with the most common foods that can trigger an allergic reaction . These foods are:
- Tree nuts (such as almonds or walnuts)
When can babies have peanut butter and other common allergens?
Before introducing any allergens, you need to know that your baby is ready for solids. When offering peanut butter and other common allergen, make sure your baby is already accepting other foods.
With that said, the early introduction of peanut and its continued presence in the diet can reduce peanut allergy later in childhood by 80% , . So we want to start adding in food allergens as soon as safely possible.
If you’re wondering when babies can have peanut butter, the suggestion is as early as 4 - 6 months old in order to protect against peanut allergy.
The National Institute of Allergy and Infectious Diseases (NIAID) suggests :
- Early peanut introduction at 4-6 months: Babies with family history of developing allergic reactions
- Peanut introduction at 6 months: Babies with moderate eczema
- No specific timeline: Babies without risk of allergic reactions. Introduction can be more in line with family and cultural practices
But these recommendations are not exclusive to peanut allergy. The early introduction of grains and fish can also protect against respiratory allergies and eczema. For example, research has found that:
- The introduction of wheat, rye, oats, or barley at 5 (or 5.5) months can help decrease the risk of asthma and allergic rhinitis 
- The introduction of fish before 9 months may reduce the risk of allergic runny nose and eczema 
It’s important that parents check with their healthcare provider before offering allergen-containing foods to their baby. If a baby already has an allergy or a family-history of allergic reactions to food, it may be best to work with an allergist to establish the safest way to approach common allergens , .
How do I know if my baby has a food allergy?
When your baby begins solids, you may want to track foods that can trigger an allergic response. This way, you can quickly spot the allergenic trigger .
An allergic reaction to food can happen immediately or hours after offering your baby an allergen.
When introducing solids, watch out for these food allergy symptoms:
- Immediately - 2 hours of eating food: Include skin (hives, rash, flushed skin) or respiratory symptoms (coughing or wheezing, difficulty breathing) . Cow’s milk, soy, and egg are the most common triggers.
- 1 - 4 hours of eating food: Digestive troubles, such as diarrhea or repetitive vomiting .
The Centers for Disease Control and Prevention (CDC) recommends introducing one single-ingredient food at a time and observing any reactions for 3 to 5 days afterwards .
However, this means your baby would take in only five to ten new foods a month, which limits food exposure in a big way. Also, a variety of food exposure during the first year helps to avoid picky eating . You may want to apply the CDC’s 3 to 5 day rule to allergens only. Work with your pediatrician to come up with the best plan for your baby’s needs.
What can I do if my baby has been diagnosed with a food allergy?
One of the most common allergies in babies is cows milk protein allergy or CMPA. This condition can affect between 2% and 7.5% of kids under the age of 12 months old , .
If your baby has been diagnosed with CMPA, it’s best that they avoid cow’s milk and other dairy products such as:
- Milk from other animals such as sheep or goat , 
- Soy-based milk , 
- Lactose-free milk, since it will still carry the milk protein 
But don’t worry. Often CMPA isn’t a forever thing.
Research has shown that close to half of children diagnosed with CMPA will eventually outgrow milk allergy during childhood . This means that you can reintroduce cow’s milk at some point during your baby’s development. However in this case, it is best to do it under the supervision of your pediatrician.
The safest alternatives for a baby diagnosed with CMPA  are:
- Breast milk (from someone that’s avoiding milk, dairy and soy)
- CMPA-formula (recommended by your pediatrician)
- Fortified pea protein milk
- Oat milk
If you decide to feed your baby plant-based milk or dairy products, check with your healthcare provider to identify the best option for your baby’s nutrition.