Milk allergy symptoms in infants can be hard to decipher. A fussy baby could have colic, or they might just be tired and cranky. When fussiness is accompanied by tummy troubles, or if your baby doesn’t want to take a bottle or shies away from the breast, the problem might be a milk allergy.

Here’s how to spot the symptoms of a milk allergy and what to do if you suspect your baby is sensitive to cow’s milk formula or breast milk.

What Is a Milk Allergy?

Allergies in general occur when the immune system mistakes a harmless substance (like pollen or dust) for a more dangerous invader (such as bacteria or viruses). It launches an attack, triggering the release of chemicals that cause allergy symptoms.

In some babies, the body mistakenly targets proteins in milk. After a baby with a milk allergy takes the bottle or drinks from the breast, they may become:

  • fussy
  • gassy
  • itchy
  • develop hives (red, itchy bumps on the skin)

Chronic Diarrhea of Infants and/or Young Children »

Cow’s milk allergies are the most common type of allergies in young children. About 2.5 percent of children under age 3 have a milk allergy, according to Food Allergy Research & Education. Babies with milk allergies are often allergic to many types of milk, including goat’s milk and sheep’s milk.

A milk allergy isn’t the same as lactose intolerance. Being lactose intolerant means the body doesn’t make enough of the enzyme lactase. Without this enzyme, the body can’t properly digest the sugar in milk, called lactose.

Lactose intolerance can cause uncomfortable symptoms such as gas or diarrhea, but it’s not life-threatening like a milk allergy. It’s rare for babies to be lactose intolerant.

Types of Milk Allergies

Immunoglobulin E is an antibody your body releases that binds to the allergen — in this case, milk protein — and triggers symptoms. Milk allergies can be immediate (IgE-mediated) or delayed (non-IgE mediated).

IgE-mediated milk allergies cause symptoms within a couple of hours the baby being exposed to milk. Non-IgE-mediated allergies stem from a different type of immune response. Symptoms start later, typically a day or more after baby drinks the milk.

Why Do Some Babies Get Milk Allergies?

Milk allergies commonly run in families. If a parent, brother, or sister has allergies or asthma, it’s likely the newborn will too.

Breastfeeding seems to offer some protection. Breastfed babies are less likely to develop milk allergies than infants who are formula-fed.

Signs Your Baby Has a Milk Allergy

Symptoms can show up immediately or hours after your baby drinks cows’ milk.

Immediate symptoms include:

  • hives
  • rash around the baby’s mouth
  • runny nose
  • swelling of the face
  • vomiting
  • diarrhea

Babies with delayed symptoms may have:

  • diarrhea or constipation
  • eczema
  • fussiness
  • gas
  • irritability

Your baby may also refuse to eat. Because these symptoms can be hard to tell apart from other common infant conditions, it’s always a good idea to call your pediatrician for an appointment.

A very severe reaction to milk, called anaphylaxis, is rare for children. However, you should be aware of symptoms of anaphylaxis, such as trouble breathing and loss of consciousness. Anaphylaxis can be life-threatening, so take your baby to the emergency room as soon as possible if you notice these symptoms.

How Your Doctor Diagnoses Milk Allergy

If you suspect your baby is reacting to milk, see an allergist. The doctor will first ask about your baby’s symptoms and health history. No single test can positively identify a milk allergy, so your doctor may order one or more of the following tests.

Blood Test

This test checks for antibodies to milk proteins in your baby’s blood. Antibodies are substances your immune system produces in response to the allergen. A high blood antibody level is a sign your child is allergic to milk. This test can also help predict whether your baby will grow out of the allergy.

Skin Prick Test

A very tiny amount of the milk protein is placed with a needle just under the skin of your baby’s arm or leg. A red bump that forms about 15 to 20 minutes later indicates a positive test result.

Patch Test

A patch containing a small amount of milk protein is placed on your baby’s skin and left there for up to two days. Red and irritated skin underneath the patch is a sign of an allergy.

Oral Challenge Test

The doctor will give your child a small amount of milk or formula to drink and watch for a reaction. 

How Is a Milk Allergy Treated?

The best way to treat a milk allergy is to avoid giving your baby any cow’s milk or product that contain it. Carefully read labels on formula and other food products you feed your baby.

Formula-fed babies should be switched to an extensively hydrolyzed formula. The milk proteins in hydrolyzed formulas are already broken down so they won’t cause an allergic reaction. Soy-based formulas are another option, although some babies are also allergic to soy.

Milk protein can be passed through breast milk. Breastfed babies can continue nursing, but you’ll have to watch your diet. Avoid eating dairy products — and possibly meat and soy too — for as long as you nurse. A dietitian can help plan a nutritious diet with alternate calcium and protein sources.

If your child is severely allergic to milk, keep an epinephrine auto-injector (EpiPen) nearby at all times. Ask your doctor which dose is right for your child’s age and weight.

Epinephrine can reverse the symptoms of a severe allergic reaction, but you should still take your child to an emergency room right away if a reaction occurs.

Can Babies Outgrow Milk Allergies?

Most children will outgrow a milk allergy by their fifth birthday. Some children can tolerate products made with highly heated milk, such as muffins or other baked goods. Other children are unable to drink milk or eat milk products for the rest of their lives.

Once your child is old enough, you may try to slowly introduce milk-based foods back into their diet. Ask your pediatrician or allergist when it’s safe to start.