Celiac disease is an autoimmune disease. It is not a food allergy, a sensitivity, or an intolerance, though it’s commonly confused with all three. When someone with celiac disease eats gluten, their immune system attacks the lining of their own small intestine, causing damage that can take years to fully heal.
What Makes Celiac Disease Autoimmune
Autoimmune diseases share a defining feature: the immune system mistakes the body’s own tissues for a threat and attacks them. In celiac disease, the trigger is a specific segment of the gluten protein called gliadin. When gliadin enters the small intestine, the immune system mounts a response that doesn’t just target the gluten. It turns against the intestinal lining itself, inflaming and gradually destroying the tiny finger-like projections called villi that absorb nutrients from food.
This self-directed attack is what separates celiac disease from a wheat allergy. In a wheat allergy, the immune system produces a different type of antibody (IgE) that triggers classic allergic symptoms: hives, swelling, wheezing, nasal itching, and in severe cases, anaphylaxis. These reactions can be serious, but they don’t cause the slow, cumulative intestinal damage that defines celiac disease. Celiac disease instead involves tissue transglutaminase IgA antibodies, which your body produces specifically in response to gluten and which signal an autoimmune process rather than an allergic one.
The Role of Genetics
Celiac disease requires a genetic predisposition to develop. More than 90% of people with celiac disease carry a gene variant called HLA-DQ2, while most of the remainder carry HLA-DQ8. These gene variants are part of the immune system’s machinery for distinguishing the body’s own proteins from foreign invaders. In people with celiac disease, that machinery misfires when it encounters gluten.
Here’s what makes genetics interesting in celiac disease: 30 to 40% of the general population carries one of these gene variants, but only about 3% of carriers ever develop the disease. Having the genes is necessary but not sufficient. Something else, likely a combination of additional genetic factors and environmental triggers, tips certain carriers over the edge into active disease. This is why celiac disease can appear at any age, sometimes decades after a lifetime of eating gluten without problems.
How It’s Diagnosed
The first step is usually a blood test that checks for tissue transglutaminase IgA antibodies. This test has a sensitivity between 78% and 100% and a specificity between 90% and 100%, making it a strong screening tool but not a perfect one. If the blood test suggests celiac disease, doctors typically confirm the diagnosis with an upper endoscopy, taking small tissue samples from the duodenum (the first section of the small intestine) to look for the characteristic damage to the villi.
One important detail: you need to be eating gluten regularly for these tests to work. If you’ve already cut gluten from your diet, the antibodies may drop and the intestinal lining may begin healing, which can produce a false negative result.
What Happens if Celiac Goes Untreated
Because the damage is gradual and internal, many people live with undiagnosed celiac disease for years. The consequences compound over time. Damaged villi can’t absorb nutrients properly, which leads to deficiencies in iron, calcium, and other essentials. Over time, this can cause bone weakness, nerve damage, skin rashes, lactose intolerance, and infertility. Some of these complications, particularly severe bone loss and infertility, may not be fully reversible even after starting treatment.
Celiac disease also clusters with other autoimmune conditions. Hashimoto’s thyroiditis is the most common, appearing in roughly 24% of celiac patients in one study. Type 1 diabetes occurs at significantly higher rates as well, with one large study of over two million people finding that celiac disease raised the risk of type 1 diabetes more than fivefold. Sjögren syndrome, psoriasis, inflammatory bowel disease, and arthritis also appear at elevated rates.
Treatment and Intestinal Recovery
The only treatment for celiac disease is a strict, lifelong gluten-free diet. There is no medication that stops the autoimmune response while you continue eating gluten. On the positive side, removing gluten works remarkably well for most people. More than 80% of those who commit to the diet see their symptoms improve or disappear entirely.
Intestinal healing, however, takes considerably longer than symptom relief. A study at the Mayo Clinic followed 241 adults with celiac disease through follow-up biopsies and found that after two years on a gluten-free diet, only about one-third had fully recovered intestinal villi. After five years, roughly two-thirds showed full recovery. Children generally heal faster and more completely than adults.
An Australian study added a sobering nuance: intestinal villi improved for the first six to twelve months on a gluten-free diet but then plateaued at levels still below those of people without celiac disease. Australia has stricter gluten-free labeling standards than the United States, so trace gluten exposure is an unlikely explanation. This suggests that for some adults, full histological recovery may be difficult to achieve even with excellent dietary adherence.
How Celiac Differs From Gluten Sensitivity
Non-celiac gluten sensitivity can cause symptoms that overlap heavily with celiac disease: bloating, fatigue, brain fog, abdominal pain. The key difference is that gluten sensitivity does not involve the autoimmune attack on the intestinal lining. People with gluten sensitivity test negative for celiac antibodies, and their intestinal biopsies look normal. They feel better when they avoid gluten, but their bodies aren’t sustaining the kind of cumulative organ damage that celiac disease causes.
This distinction matters because celiac disease carries long-term health risks that gluten sensitivity does not. The intestinal damage, nutrient malabsorption, bone loss, and association with other autoimmune conditions are specific to celiac disease. If you suspect you react to gluten, getting tested before eliminating it from your diet is the most reliable path to knowing which condition you’re dealing with.