3 Ways to Tell Lactose Intolerance Symptoms from a Dairy Allergy (Yes, There's a Difference)

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Lactose intolerance is caused by the stomach’s inability to digest lactose, which is a sugar found in milk.

When your child is affected by dairy, it’s often originally diagnosed as lactose intolerance, a common intolerance among babies and one that can also develop around age two. But if you’ve tried lactose-free dairy and still have issues, your child may have a dairy allergy! Learn our three ways to tell the difference between lactose intolerance symptoms and a full-on dairy allergy. If you or your child live with either lactose intolerance or dairy allergy, leave a comment with your favorite dairy-free recipe or cooking substitution.

What’s the difference between dairy allergy and lactose intolerance?

The primary difference between lactose intolerance and a milk allergy is that a milk allergy is a function of the immune system. The immune system identifies milk proteins as invaders and releases immunoglobulin E (IgE) antibodies into your child’s bloodstream. The antibodies release histamine, which causes milk allergy symptoms.

Lactose intolerance is caused by the stomach’s inability to digest lactose, which is a sugar found in milk. The lactase enzyme isn’t produced, or not enough is produced so milk cannot be properly absorbed.¹ This leads to digestive issues.

Some children eventually outgrow an allergy, particularly if their gut and immune system is allowed time to heal.

3 Ways to Tell Dairy Allergy from Lactose Intolerance

1. Symptoms: Lactose intolerance symptoms and a dairy allergy can be similar.² Diarrhea, stomach irritation and gas are common to both. However, with a milk allergy, your child can also experience skin irritation and hives, wheezing, runny nose and watery eyes.

When my 3-year-old was originally diagnosed with lactose intolerance our biggest worry was the diarrhea, so while she also had skin irritation and mild hives, our focus was on the extremely difficult potty training. That led her doctor to a lactose intolerance diagnosis. She later determined our daughter actually has a milk allergy. If your child has skin and breathing symptoms, ask your doctor about milk allergy. If you find out milk is a no-no, don’t worry— you have tons of delicious dairy-free meals to look forward to, like these six rockin’ smoothies, for example.

2. Lactase: Have you supplemented your child’s diet with lactase tablets or liquids in their dairy? If so and symptoms have stopped, it is likely intolerance. If so and symptoms continue, your child may have milk allergy.

In the case of an allergy, your child should avoid eating dairy completely. Some children eventually outgrow an allergy, particularly if their gut and immune system is allowed time to heal. However, others have the allergy for a lifetime.

If you’ve determined it’s lactose intolerance, those with intolerance can typically eat a variety of milk products, including buttermilk, cheeses, fermented milk products (such as yogurt), ice cream, and lactose-free milk. But don’t overdo it and always consult your child’s doctor first.

3. Whey: Some children thought to have total milk allergy may actually be allergic to to whey.³ In this case, they will be able to eat hard cheeses without symptoms. If your child’s symptoms are not severe, you can try adding hard cheeses back to their diet after two weeks of a dairy elimination diet. If symptoms return, your child likely has a total milk allergy. If not, they may be allergic to whey and can continue to eat hard cheeses like parmesan.

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