How do I know if my baby is allergic to a food?

Babies experiencing an allergic reaction to something they ate will often break out in a rash or have difficult bowel movements. Any severe reaction should trigger an immediate call to 911!

When it comes to starting your baby on different foods, you've probably heard the advice, "Start one new food every few days, so if your baby has an allergic reaction, you will know which food caused it." But what exactly does an allergic reaction look like, and does it vary by age?

In very young babies, including those still on breast milk or formula, an allergy usually manifests as a skin rash or a dramatic change in stools. These babies often have severe eczema that won’t respond to the usual treatment with moisturizers and cortisone. They may also have uncomfortable bowel movements with blood or mucus in the stool.

In babies who are starting cereal and other solids, allergies often appear as rashes that appear after eating the offending food. Your baby may or may not appear fussy. If your baby develops a diaper rash after trying a new food, avoid that food until your next scheduled well-child check-up, and then to bring it to your doctor’s attention. There are blood tests that can detect some allergies, but often the food in question can be safely reintroduced at a later time.

Lastly, any reaction that results in difficulty breathing, such as wheezing, requires emergency attention. Please do not delay in calling 911!


  1. When I started my son on whole milk at 12 months, he would get a rash every time he had a bowel movement. The rash would only appear where the poop touched his skin. I stopped whole milk, and the rash stopped. At his 15-month well check, his doctor said to try again and if we had the same issues, we could look into other options. He has been drinking 1/2 breast milk 1/2 whole milk for about a week now with no rashes! I’m glad he seems to have grown out of whatever “allergy” he had!

  2. I feel so fortunate we don’t have any allergies to food. There are so many children out there with peanut allergies and I hate it for them! My youngest had a milk allergy for the first year of his life and I’m so grateful he grew out of it. I do wonder if my 4 year old is allergic to watermelon. He gets a red rash (little bumps) around his mouth and on his chest when the juice drips. Anyone know? That is the only reaction he has to it.


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