Is It a Milk Allergy or Lactose Intolerance?

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Lactose intolerance often gets confused with a milk allergy, but they’re not the same thing … like, at all.

A milk allergy means you’re allergic to a milk protein, whereas lactose intolerance means you aren’t able to digest the sugar found in milk.

When someone with a milk allergy ingests a milk product, their immune system feels like it’s under attack, and releases antibodies that trigger an allergic reaction – which can range from hives and wheezing, right up to to vomiting, diarrhea, an asthma attack, or anaphylaxis.

Someone with lactose intolerance is not allergic to any part of the milk, but they’re unable to digest the sugar found in milk. If they eat or drink a product containing milk, they can be plagued with gastrointestinal issues, like stomachaches, diarrhea, gas.

milk allergy or intolerance

Since stomachaches and diarrhea are potential side effects of either a milk allergy or intolerance, people get confused and think of them as the same condition.

We suspected our daughter, Charlotte, had a milk allergy around her first birthday, because she would have terrible stomach pain and diarrhea after ingesting milk or ice cream. But we had her tested, and she wasn’t allergic – just suspected to be lactose intolerant.

The trouble with lactose intolerance is that there isn’t a test for it – it’s just a matter of cutting milk out completely, and seeing if the symptoms improve. So we started giving her rice milk (fail), almond milk (fail), and ultimately lactose-free milk (win) – which is cow’s milk with the lactose (milk sugar) removed.

Charlotte can eat small amounts of hard cheese and yogurt without a problem, so it really hasn’t been a big deal (unlike her egg allergy). We keep her away from ice cream, whipped cream, cow’s milk, and anything else that’s straight-up lactose, basically.

If someone were to feed her ice cream, she wouldn’t be in any danger – other than, uh, needing to spend some serious time on the potty later on. But this experience has made me more cautious of the kids out there who do have actual milk allergies.

Despite the growing number of people with severe milk allergies, you still hear of people proclaiming they’re “allergic” to milk – when, really, they’re just lactose intolerant and don’t want to get the runs out in public. But the word “allergy” shouldn’t be thrown around. A child with a severe milk allergy couldn’t even come in contact with a milk product – like sidewalk chalk containing casein – without getting a reaction.

So just a reminder, that if you’re hosting a playdate or a party, always ask if anyone has an allergy or an intolerance. Never assume that “just a little” of something is probably fine, and never confuse a milk allergy with lactose intolerance.

Basically, it’s the difference between having a potentially fatal peanut allergy, and passing on the Peanut Butter Fudge Crunch ice cream so you’re not running to the bathroom at the beach.

Heather Laura Clarke, a contributing writer at Scratch or Sniff, lives in Nova Scotia, Canada, with her high-school sweetheart husband, seven-year-old son, and five-year-old daughter. She writes for newspapers and magazines across Canada and the U.S., and blogs about her family life at Heather's Handmade Life. Follow her adventures on Twitter or Instagram.

11 Comments to Is It a Milk Allergy or Lactose Intolerance?

  1. Tiffany

    Excellent, Heather! Thanks so much for breaking it down. I knew there was a major difference between lactose intolerance and milk allergy, but had no idea why. Nice to know the “why” behind it.

    • Thanks, Tiffany! I think a lot of people confuse the two. I had friends growing up who were lactose intolerant but declared they were “allergic” because they honestly thought they were.

  2. Roo Ciambriello

    I know this wasn’t your intent, but I could totally go for some ice cream right now.

    On a serious note, thanks for outlining the difference!

  3. Julie`

    Just a correction — there is a test for lactose intolerance. I had it done last year. It consists of fasting, drinking a high lactose solution, and then getting blood drawn every half hour for the next 2 hours. The normal body should break down lactose into glucose and galactose, so the draws are actually looking for the presence of glucose in your blood, indicating that your body is digesting the lactose appropriately.

    It’s not comfortable — you have a new needle stick for each draw — but it is a surefire way to diagnose.

    • Wow, that’s interesting, Julie! I’ve never heard of anyone getting the test. Our family physician and allergist told us there was not a test, but maybe they say that because it wouldn’t be a viable option for our two-year-old. Good to know!

      • Kristina

        There’s actually another test too, a hydrogen breath test. I had this done when I was a child and, being that I was confirmed to be lactose intolerant, I ended up with extremely severe stomach pains that evening. It was awful. :( Funny, I’ve never had a milk allergy, but my two daughters do and now that my teenage daughter has outgrown her milk allergy, she seems to be developing a sensitivity to lactose.

  4. When i was a child, i had a severe Milk Allergy. I still remember, in pre-school, we were “finger painting”… with chocolate pudding! I broke out in major hives from my fingers to my shoulders. I’m now 31, and have a Greek Yogurt almost every morning for breakfast, LOVE Brie and Mozzarella, and don’t freak out if there aren’t any non-dairy options to put in my coffee. I no longer tell people i am allergic, but that i am lactose intolerant. There is definitely a limit to my cow’s milk-consuming-ability (i can only stomach ONE spoonful of ice cream, and i generally avoid cheeses and anything creamy), but the evolution of my allergy has been pretty remarkable. My younger sister, on the other hand, is still highly allergic to Dairy and carries 2 Epi-pens with her at all times. Why mine changed and her’s did not is a big family mystery.

    Thank you for this article!

    • That’s wonderful that your milk issues have gotten so much better, Hannah! Intolerances are definitely preferable to allergies. Hopefully things will turn around for your sister, too!

      • She just had her 1st child in July, so now we’re all curious if she’ll also be allergic. Obviously, after both of our experiences, we’re approaching it very cautiously and strategically.

        • That’s smart, Hannah! Fingers crossed she’s a tiny cyborg with zero allergies, like Roo’s youngest daughter! :)

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