Lactose intolerance affects millions of people worldwide—sometimes without them even realizing it. In this article, we’ll explore eight common ways your body might be signaling that lactose could be the source of your discomfort.
THIS CONTENT IS FOR INFORMATIONAL PURPOSES ONLY AND SHOULD NOT BE USED AS A SUBSTITUTE FOR MEDICAL ADVICE.
CONSULT YOUR DOCTOR FOR GUIDANCE ON YOUR HEALTH AND MEDICAL CONDITIONS.
Unexpected Symptoms of Lactose Intolerance
While digestive issues are the most well-known symptoms, some individuals with lactose intolerance also report experiencing headaches, fatigue, brain fog, muscle and joint pain, mouth ulcers, urinary problems, and even eczema.
Mouth Ulcers
Dairy products like milk, cheese, and yogurt have been associated with the development of canker sores. Some experts believe that certain proteins in cow’s milk may trigger mouth ulcers in sensitive individuals due to an adverse immune response.
If you frequently suffer from mouth sores, consider cutting out dairy, particularly products made from animal milk. Instead, experiment with dairy-free alternatives such as soy milk, oat milk, and vegan cheese to see if they help reduce flare-ups.
Swelling and Allergic Reactions
Dairy allergies can cause symptoms that go beyond digestion, affecting the skin and respiratory system. Common reactions include:
- Rashes
- Hives
- Swelling, particularly around the lips and face
- Wheezing
- Tightness in the throat
- Difficulty swallowing
In some cases, particularly in infants, blood may also appear in the stool.
More severe reactions, such as throat swelling and difficulty breathing, could indicate anaphylaxis—a serious, potentially life-threatening allergic response. Anaphylaxis can develop within minutes of consuming a trigger food, though delayed reactions are possible. If this occurs, seek immediate medical attention. If epinephrine is available, administer it right away and call emergency services. If not, head to the nearest emergency room without delay.
Digestive Issues: Diarrhea or Constipation
Lactose intolerance happens when the body struggles to break down lactose, the sugar found naturally in milk. This can lead to digestive discomfort, including diarrhea after consuming dairy. While not usually dangerous, it can be highly uncomfortable.
However, lactose intolerance doesn’t always cause diarrhea. Some individuals—particularly those whose gut bacteria produce methane instead of hydrogen—may experience constipation instead. Research suggests that methane production can slow down intestinal movement, making constipation a more prominent symptom in about one-third of lactose-intolerant individuals.
Bloating
Bloating is another common symptom of lactose intolerance in both children and adults. This occurs when the body lacks sufficient lactase, the enzyme responsible for breaking down lactose into simpler sugars for absorption.
Undigested lactose travels to the colon, where gut bacteria ferment it, leading to gas buildup and bloating.
Headaches and Fatigue
Some symptoms of lactose intolerance go beyond digestive issues. Many individuals report experiencing headaches, fatigue, back pain, brain fog, and general tiredness. Others may also struggle with dizziness, sleep disturbances, and an overall sense of malaise.
These lesser-known symptoms could be linked to the body’s inability to properly process lactose, triggering inflammatory or metabolic responses in sensitive individuals.
Gas and Flatulence
When lactose remains undigested in the small intestine, it moves to the colon, where gut bacteria break it down.
This fermentation process produces gases like hydrogen, methane, and carbon dioxide, which can lead to bloating, cramping, and excessive flatulence.
Muscle and Joint Pain
Lactose—the sugar found in dairy—may also contribute to muscle and joint discomfort. Normally, the enzyme lactase breaks down lactose in the small intestine. However, most people experience a decline in lactase production after infancy, making digestion more difficult.
Even for those who can still digest lactose, it is quickly converted into glucose, which may disrupt gut bacteria, elevate blood sugar levels, and trigger inflammation. Whether due to poor digestion or lactose’s metabolic effects, this can lead to joint pain and inflammation—something most people want to avoid.
Abdominal Cramps and Pain
One of the most prevalent symptoms of lactose intolerance is abdominal pain and cramping, which typically occurs within a few hours after consuming dairy.
Additionally, if you experience symptoms of lactose intolerance, it may be worth considering whether gluten intolerance is also playing a role.
