Starting solids is a time of curiosity, joy, and (let’s be honest) a bit of uncertainty. As your baby reaches for their first tastes—perhaps a smear of peanut butter, a spoonful of yogurt, or a bite of scrambled egg—you might find yourself wondering: What if they’re allergic? How will I know?
Food allergies are a growing concern among parents, and it’s easy to see why. Between cautionary labels, online anecdotes, and evolving guidelines, the line between staying informed and feeling overwhelmed can get blurry. But here's the good news: most babies tolerate new foods beautifully, and early, thoughtful introduction of potential allergens can actually help prevent some allergies from developing.
Still, it's empowering to know what to look for—and what to expect. We’ll cover what foods most commonly cause allergic reactions, as well as how to tell the difference between a food allergy, an intolerance, and a lesser-known condition called FPIES. Whether you're here to understand what might cause a reaction or simply to feel more grounded before that next messy mealtime, you’re in the right place.
What Is a Food Allergy—And What’s Not?
Oftentimes, when a baby or child reacts to a food, we say they have a food allergy. But not all reactions are true food allergies. Understanding what kind of reaction your child is having can help guide your next steps.
IgE-Mediated Food Allergies
IgE-mediated food allergies are what most people think of when they hear "food allergy." This happens when a baby’s immune system treats a food protein like a threat. Reactions typically occur quickly—within minutes to a few hours—and can include hives, swelling, itching, vomiting, and difficulty breathing. Even small amounts of the allergen can trigger a response, and these allergies usually require strict avoidance of the trigger food and access to emergency medication like epinephrine.
Food Intolerances
Food intolerances are different. They don’t involve the immune system in the same way. Instead, they affect the gastrointestinal system and tend to be dose-dependent—the more a child eats, the worse the symptoms may be. Common signs include abdominal pain, gas, diarrhea, and headaches. These often don’t require full avoidance, just moderation.
Food Protein-Induced Enterocolitis Syndrome (FPIES)
FPIES is less widely known but increasingly recognized. It involves a delayed immune response in the gastrointestinal tract. Symptoms like vomiting, diarrhea, lethargy, and dehydration typically appear 1-4 hours after eating the trigger food. It can be mistaken for a stomach bug. Most children outgrow FPIES, but they will need to avoid the trigger foods until they do.
The Top 9 Common Food Allergens in Children
While any food can technically cause an allergy, nine are responsible for about 90% of reactions:
Milk: Common early allergen, especially if formula-fed. Found in dairy products and many packaged foods. Different from lactose intolerance.
Eggs: Reactions may occur to either the white or yolk. Found in baked goods and sauces.
Peanuts: A major cause of anaphylaxis. Present in peanut butter, sauces, and baked goods.
Tree Nuts: Includes almonds, cashews, and more. Found in nut milks, bars, and pesto.
Wheat: Often confused with gluten intolerance. Found in bread, pasta, and baked goods.
Soy: Common in processed foods and formulas. Soy lecithin is usually tolerated.
Fish: More common in adults but can occur in infants. Includes salmon, tuna, etc.
Shellfish: Includes shrimp, crab, and mollusks. Often presents later in life.
Sesame: Newly added to the list. Found in tahini, sesame oil, and baked goods.
Again, a baby can react to any food. Most tolerate these just fine. It’s about being aware, not afraid.
Other Foods That May Cause Reactions
FPIES Triggers
Common FPIES triggers include milk, soy, rice, and oats. Others may include banana, corn, sweet potatoes, peanuts, eggs, and shellfish.
Common Food Intolerances
- Lactose Intolerance: Caused by low lactase enzyme levels. Leads to bloating and diarrhea.
- Gluten Intolerance: Not celiac. Causes fatigue and abdominal pain.
- Fructose Intolerance: Similar to lactose. Found in fruit and sweeteners.
- FODMAPs: Fermentable carbs that cause GI symptoms. Includes onions, garlic, apples, beans.
- Additives/Preservatives: Sulfites, MSG, and dyes can cause symptoms in sensitive children.
These typically require reducing the food, not fully eliminating it.
What to Do About Introducing Allergenic Foods
While it may feel intimidating, early introduction of allergenic foods may help prevent allergies. Here are a few steps to make it feel safer:
- Make sure baby is well before introducing a new food.
- Start with a small amount mixed into a well-tolerated food.
- Offer during a time when you can monitor for at least 2 hours.
-
Once tolerated, keep the food in regular rotation.
Spotting a Reaction: When to Take Action
- Mild signs: Rash, fussiness, mild GI symptoms. Notify your pediatrician.
- Moderate signs: Vomiting, diarrhea—especially if repetitive or severe.
- Severe signs: Trouble breathing, swelling, bluish lips. Call emergency services.
If your baby has ongoing symptoms, consult a pediatrician or allergist before reintroducing foods. If there is a family history of allergies or you're unsure, seeking guidance is a proactive step.
Final Thoughts: You’re Doing Better Than You Think
Introducing new foods to your baby—especially the ones labeled as "allergens"—can feel like walking a tightrope between nourishing curiosity and managing fear. But here’s what matters most: you’re here, you’re learning, and you’re leading with love.
While food allergies, intolerances, and conditions like FPIES can sound intimidating, most babies handle the introduction of new foods with ease. And when reactions do happen, knowing the signs and having a plan in place helps you respond with clarity instead of panic.
Let this be your permission slip to take things one bite at a time. You don’t have to be perfect. You just need to be present—and trust that your growing knowledge (plus your gut instinct) are powerful tools.
If you’re ever unsure, it’s okay to pause. Talk to your pediatrician. Reach out to a dietitian or allergist. You’re not alone in this journey—and asking for guidance is a sign of strength, not failure.
So whether today is peanut butter day or sweet potato day, remember: you’ve got this.