How to Tell if Your Dog is Lactose Intolerant

Human babies get their nutrients from milk. In order to break down the nutrients found in milk, babies need a significant amount of an enzyme called lactase. However, as the babies grow up and start eating soft and, eventually, solid food, the body cuts back on lactase production since it no longer has much function.

That is why almost 65 per cent of the human population have reduced ability to digest milk after infancy. In other words, most people are lactose intolerant.

This is true for most mammals, dogs included. Once they’ve been weaned, dogs can start showing symptoms of lactose intolerance when they ingest a significant amount of milk and other dairy products.

So how do you know if your dog is lactose intolerant? Here’s how to tell.

Sudden Lack of Appetite

Are they lethargic and are keeping away from their food bowls? Has your pooch not eaten anything in half a day when they normally get overexcited over food? Test their attentiveness by baiting them with some exciting treats. If they’re still not interested, it’s not just lethargy anymore.

The sudden lack of appetite is a telltale sign that your dog’s stomach and gastrointestinal (GI) tract may be upset. Look for the culprit in their most recent diet. If milk or any milk-derivative ingredient has been ingested, it’s possible that your pooch is lactose intolerant and needs immediate care.


Vomiting is a natural reflex that allows the dog to get rid of poisons or toxins that have been ingested. For most dogs, vomiting incidents are normal, especially if they’re aggressive and active chewers. But if they are vomiting intensely and frequently, after lapping a bowl of milk, it’s possible that their gut has been affected by the ingested product.

A clear way to tell if your dog is about to vomit is when they start licking surfaces or drool a lot.

Stomach Bloating

A bloated stomach is the effect of gas buildup in the GI tract. This gas is produced by bacteria within the intestines when they digest dietary sugars like lactose, which reaches the colon undigested.

Signs that your dog is bloated include pacing, unsuccessful vomiting or trying to vomit but only bringing up foamy saliva, and restlessness.


Your pooch passing gas is often the cause of fun, not alarm. However, if it occurs more often than is normal, it only makes sense to suspect something is probably not sitting right in their gut. If dairy has been consumed in the past few hours, stop the feeding immediately.

Diarrhoea or Loose, Watery Stool

Because there’s not much lactase to digest milk in most of an adult mammal’s body, the excess undigested sugar in milk, called lactose, passes through the digestive system unprocessed. Water attracts sugar in the digestive tract, which explains the watery or loose stool.

If you notice diarrhoea hours after your dog consumes milk, it’s a sign that your dog may need to cut back on the milk diet.

Word of Warning: Lactose Intolerance Can Look a Lot like Dairy Allergy

A lot of the symptoms of lactose intolerance are also present in dairy allergy. However, one important difference is the presence of skin problems (usually hives) that come with allergies.

If your dog constantly licks or scratches their ears, paws, or behind, alongside noticeable redness in the skin, it’s possibly caused by allergies to dairy and not just intolerance. Other symptoms include difficulty breathing and, oftentimes, swelling of the face.

What to Do When Symptoms Show

If you notice symptoms of lactose intolerance in your pooch, immediately halt the dairy diet for a few weeks or so to see if the symptoms fade. Otherwise, visit the veterinarian immediately to have professional tests conducted and to get to the root of the problem.

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