Egg allergies are the second-most common food allergy in babies. But what exactly is an allergy to eggs? And what does it look like if your baby has an egg allergy? Here’s what we know about egg allergies and babies. 

What is an Egg Allergy?

In an egg allergy, your baby’s body mistakes the proteins in an egg for a dangerous parasite.  

When most people eat eggs, their bodies simply break it down as food with no issue. 

However, some babies’ immune systems decide the protein in egg is dangerous. This is called sensitization. Once your baby’s body decides something is a threat, it creates IgE antibodies for it. IgE antibodies act like a security alarm so that if your baby’s body sees egg again, it calls up the troops.

Strangely, some babies will be sensitized to egg, meaning that the alarm system is there, but when they eat eggs, the alarm is ignored.

An allergy is when your baby’s body hears that alarm of IgE antibodies and wakes up the fighter cells. Those cells respond to the “attack” by releasing histamine and other chemicals. 

These chemicals perform tricks like heating up your baby’s body, making your baby itch and your baby’s skin swell, building up mucus, and making your baby cough or throw-up, all in an attempt to get the harmful egg out and prevent more from getting in.

Illustration of an allergic reaction in the cells

So why does your baby’s body mistake egg for a harmful substance?

We don’t know, but we have some theories that are all being studied:

  • The egg protein happens to enter the body at the same time as a parasite and the body thinks the egg IS the parasite. The next time it sees the egg, the body attacks.
  • The egg protein got through the skin before it went to the stomach, and the body tends to call anything that gets through the skin a threat. When your baby then eats egg, the body makes a mistake and attacks. (This is called the Dual Exposure Hypothesis).
  • A protective lining is missing from your baby’s intestines, so egg protein “leaks out" where it shouldn’t and this makes the body think it’s a threat.
  • Your baby’s body is missing friendly bacteria that live in the gut (called the microbiome). In most people, these friendly bacteria either tell your baby’s body “I’ve seen this before, stay cool,” or even create the protective mucus lining of the intestines. But without those friendly bacteria, no one is there to tell your baby’s body not to overreact. 

Cooked/Raw Egg vs Baked Egg Allergy 

To make things more confusings, an “egg allergy” is actually a group of several possible allergies to different proteins in the egg. A person can be allergic to one or more egg proteins.

 The most common egg proteins that babies are allergic to are found in the egg whites, meaning most babies actually have an egg white allergy. The two proteins in egg white that cause allergies are:

  1. Ovalbumin (OVA) also called Albumin / Albumen
  2. Ovomucoid (OVM)

People can also, much more rarely, be allergic to other egg white proteins like ovotransferrin, ovomucin, lysozyme, and ovoglobulin.  

The egg yolk is made of totally different proteins, which do not seem to cause allergies very often, even though some protein from the white can get into the yolk and vice versa.

Of the two major egg white proteins, babies can be allergic to OVA only, OVM only, or both OVA and OVM.

Both OVA and OVM are found in a raw egg, scrambled eggs, omelettes, pancakes, most frittatas, etc.

ONLY OVM is found when the egg has been baked for 20 mins. Baked eggs are typically found in cakes, muffins, flan, etc. When an egg is baked at 350 degrees for 20minutes or more, the OVA protein breaks apart while the OVM protein stays around.  

Babies with an OVM protein allergy cannot eat any egg, no matter how it has been cooked.

Babies with an OVA-only allergy can eat baked egg because the protein they are allergic to is broken down. They cannot eat raw, scrambled, or lightly cooked eggs. Babies with OVA-only allergy have to be careful eating foods if they do not know how it was cooked. 

What about the yolk? Babies with an egg allergy have to treat egg yolks the same as egg whites because the proteins from the egg white can be found in tiny amounts in the yolk. Babies with OVA-only allergy can eat baked egg yolk, but babies with OVM only or OVA + OVM allergy can’t eat egg yolk raw, cooked, or baked. 

What Does It Look Like If My Baby Has An Egg Allergy?

The symptoms of an egg allergy in babies can look really different than one in an older child or adult. 

Infants with allergic reactions to eggs typically only get hives and vomit. It is almost unheard of for babies under 6 months to have a life-threatening (breathing or fainting) response to food. 

In fact, the signs of an egg allergy in babies are so “mild” that they can seem very similar to a cold and may take a few minutes to an hour to show. 

REMINDER: People can be allergic to anything. Whenever you introduce any food for the first time, do it when you or another caregiver will be around your baby for the next 2 hours. Don’t feed your baby a new food and then hand them off to someone else who wouldn’t know what they ate.

Whenever two body systems are affected (skin hives AND vomiting / diarrhea), immediately call 911. 

The most common symptoms of an allergic reaction to eggs in a baby under 12 months are:

  • Skin hives (95% of reactions): These are red bumps or patches that are itchy. Scratching this itchy skin can lead to eczema.
  • Redness around the mouth or chin.
  • Swelling of the face, including puffiness around the eyes (36%).
  • Runny or stuffy nose. Sometimes with clear discharge, redness, and itchiness of the nose.
  • Vomiting (89% of reactions). Your baby throws up (more than standard spit up) within a couple hours after eating eggs.
  • Diarrhea. Particularly smelly, funny colored, or more than normal poop. 

Redness around baby's mouth from allergic reaction

Redness around the mouth from an allergic reaction

Swelling under baby's eye from allergic reaction

Swelling under the eye from an allergic reaction 

FAR less common (0-9% of reactions) in babies under the age of 1, but much more likely in toddlers and children are:

  • Swelling of the mouth, including the lips and possibly the tongue.
  • Wheezing and coughing.
  • Temperature less than 97 degrees or greater than 101.
  • Swelling in the throat that presents as difficulty swallowing.
  • Weak heart pulse.
  • Fainting. 

A study showed that severe symptoms in babies under 12 months are extremely rare. The younger your baby, the less likely it is they'll have a severe reaction.

Severity of allergic reaction by age

If you notice any of the above symptoms, mild or severe, call your doctor immediately. It’s always good to inform your doctor and check in whenever you're worried about your baby.