Neither gluten nor dairy is universally “more inflammatory” than the other. They trigger inflammation through different biological pathways, affect different people, and show up in different parts of the body. Gluten has a more direct route to systemic inflammation through its effect on gut permeability, while dairy drives inflammation primarily through hormonal signaling and, in some people, immune reactions to specific milk proteins. Which one matters more depends entirely on your own biology.
How Gluten Triggers Inflammation
Gluten’s inflammatory potential starts with a protein fragment called gliadin, which your body cannot fully digest. These indigestible fragments bind to a receptor on intestinal cells and trigger the release of a protein called zonulin. Zonulin essentially unlocks the tight seals between cells lining your gut, increasing intestinal permeability, a condition often called “leaky gut.” Once those seals loosen, bacteria, toxins, and undigested food particles can slip through the gut wall and into surrounding tissue, where they provoke an immune response.
What makes gluten particularly potent is the chain reaction that follows. Your immune system responds to these escaped particles by producing inflammatory signaling molecules, including TNF-alpha and interferon gamma, both of which further open the gut lining. This creates a self-reinforcing cycle: more permeability leads to more immune activation, which leads to more permeability. Gluten and bacterial overgrowth have been identified as the two most powerful triggers of zonulin release, making gluten a uniquely efficient driver of this process.
Beyond gut permeability, gluten proteins share structural similarities with certain human tissues, including the protective coating around nerves and pancreatic cells. This resemblance, called molecular mimicry, can cause the immune system to mistakenly attack the body’s own tissues. This mechanism has been linked to autoimmune conditions like multiple sclerosis, celiac disease, and a rare neurological condition called neuromyelitis optica.
How Dairy Triggers Inflammation
Dairy’s inflammatory effects operate through a different set of mechanisms, and they vary significantly depending on the type of dairy you consume. One major pathway is hormonal. Milk consumption raises levels of insulin-like growth factor 1 (IGF-1), a hormone that promotes cell growth and activates inflammatory signaling cascades throughout the body. Each additional 200 grams of milk per day (roughly one glass) is associated with IGF-1 levels about 10 micrograms per liter higher than baseline. Elevated IGF-1 stimulates oil glands in the skin, which is one reason dairy has a well-documented link to acne, and has also been associated with increased prostate cancer risk.
The protein composition of milk matters too. Most conventional cow’s milk contains A1 beta-casein, a protein variant that triggers a measurably different immune response than the A2 variant found in some heritage breeds and goat’s milk. Animal studies show that A1 casein significantly increases markers of intestinal inflammation, activates immune pathways through toll-like receptors (part of your innate immune defense system), and raises levels of antibodies associated with allergic and inflammatory responses. A2 casein does not produce the same effects, which suggests that not all dairy is equally inflammatory.
Lactose intolerance adds another layer. When undigested lactose ferments in the colon, it produces gas, bloating, and localized irritation, but this is a digestive problem rather than a true inflammatory immune response. The distinction matters: lactose intolerance causes discomfort, while casein-driven inflammation involves your immune system attacking what it perceives as a threat.
The Skin Connection
If your concern is inflammatory skin conditions like acne, dairy has a stronger and more consistent research trail. A systematic review of 23 studies found that 70% linked at least one dairy food item to acne development or increased severity. The mechanism is largely hormonal: dairy raises insulin and IGF-1, which stimulate oil production and create conditions favorable for breakouts. This association is strongest in Western populations, possibly due to higher baseline dairy consumption.
Gluten’s relationship with skin inflammation is less straightforward. Outside of celiac disease, where a specific blistering skin condition called dermatitis herpetiformis is well established, the evidence connecting gluten to acne or general skin inflammation in people without celiac disease is limited. If your skin is your primary concern, dairy is the more likely culprit.
Systemic vs. Localized Effects
One useful way to think about this comparison is scope. Gluten’s inflammatory effects tend to be systemic, meaning they can affect multiple organ systems once gut permeability increases. When the gut barrier breaks down, inflammatory molecules circulate through the bloodstream and can contribute to joint pain, brain fog, fatigue, and autoimmune flares far from the digestive tract. This is why people with gluten sensitivity often report symptoms that seem unrelated to digestion.
Dairy inflammation tends to be more targeted, at least initially. Its hormonal effects concentrate in tissues sensitive to IGF-1 and insulin, like skin and reproductive organs. Its immune effects from casein tend to center in the gut. That said, chronic gut inflammation from any source can eventually become systemic, so the distinction isn’t absolute.
How Many People Are Affected
Roughly one in ten people worldwide, about 10.3%, self-report sensitivity to gluten or wheat outside of celiac disease. However, diagnosing non-celiac gluten sensitivity remains difficult. There are no reliable biomarkers for it, and its symptoms overlap heavily with irritable bowel syndrome and other gut-brain disorders. It remains a diagnosis of exclusion, meaning doctors rule out celiac disease and wheat allergy before arriving at it.
Dairy intolerance is far more common globally. Estimates suggest that 65 to 70% of the world’s adult population has reduced ability to digest lactose after infancy, though prevalence varies dramatically by ethnicity. Northern European populations retain lactose tolerance at much higher rates than East Asian, West African, or Indigenous American populations. When you add casein sensitivity on top of lactose intolerance, the total number of people who react poorly to dairy is substantially larger than those affected by gluten.
Testing With an Elimination Diet
Because there is no single blood test that reliably identifies gluten or dairy sensitivity (outside of celiac disease and milk allergy), the most practical approach is a structured elimination diet. The standard protocol involves removing the suspected food completely for one to three months, then reintroducing it and monitoring symptoms. If symptoms improve during elimination and return during reintroduction, you have a clear signal.
One important detail: inflammatory reactions from a single exposure to a trigger food can persist for up to two weeks after you eat it. This means that a brief elimination of just a few days won’t give you useful information. You need at least several weeks of strict avoidance before you can fairly assess whether the food was contributing to your symptoms. Many people find it helpful to eliminate both gluten and dairy simultaneously, then reintroduce them one at a time with at least two weeks between each reintroduction, so you can isolate which one (or both) is the problem.
If you try removing one and feel no different after three months, it’s reasonable to bring it back and test the other. Some people are sensitive to both, some to neither, and some to only one. Your individual response is the only metric that ultimately matters in deciding which, if either, to avoid long term.