Celiac disease develops when someone with a specific genetic predisposition eats gluten, and their immune system attacks the lining of the small intestine instead of ignoring the protein. It affects roughly 1% of the global population, but you can’t “catch” it or develop it from eating too much bread. The disease requires a combination of inherited genes, gluten exposure, and often an environmental trigger that flips the switch.
It Starts With Your Genes
Nearly all people with celiac disease carry one of two gene variants known as HLA-DQ2 or HLA-DQ8. About 90% of celiac patients have the DQ2 variant, while another 5% to 10% carry DQ8. Fewer than 0.5% of celiac patients in Europe have neither gene. These genes are a prerequisite for the disease, which means if you don’t carry them, your chance of developing celiac disease is extremely low.
Here’s the catch: carrying the gene doesn’t mean you’ll get the disease. Roughly 55% of the general population without any family history of celiac disease carries one of these gene variants. Yet only about 1% of people overall develop the condition. So the genes are necessary but far from sufficient. Something else has to go wrong.
What Happens Inside Your Body
When you eat foods containing wheat, barley, or rye, your digestive system breaks down the gluten protein into smaller fragments. In most people, these fragments pass through the gut without incident. In someone with celiac disease, those undigested gluten fragments slip through the intestinal lining into the tissue underneath, where an enzyme modifies them chemically. This modification is the critical step: it changes the gluten fragments just enough that the immune system recognizes them as a threat.
Immune cells then present these modified gluten fragments to the body’s defense system, which launches a full inflammatory attack. One branch of the immune response sends out signals that activate killer cells, which physically damage the intestinal wall. Another branch triggers the production of antibodies against the body’s own tissue. The result is progressive destruction of the tiny finger-like projections (called villi) that line the small intestine and absorb nutrients. This is why celiac disease causes malnutrition, anemia, and bone loss even in people who eat a full diet.
Family History Is the Strongest Risk Factor
If a parent, sibling, or child has celiac disease, your risk jumps dramatically. Up to 20% of first-degree relatives are affected by the disease, compared to 1% of the general population. That’s a twenty-fold increase in risk, making family history the single most important factor in predicting who develops celiac disease.
The shared genetic overlap with other autoimmune conditions matters too. About 90% of people with type 1 diabetes carry either HLA-DQ2 or HLA-DQ8, and roughly 4% of type 1 diabetics also have celiac disease. Autoimmune thyroid conditions like Hashimoto’s thyroiditis and Graves’ disease show a similar pattern: people with celiac disease are about three times more likely to develop thyroid disease than the general population, and up to 26% of celiac patients show blood markers of thyroid autoimmunity. Overall, about 15% of people with celiac disease have at least one other autoimmune condition.
Environmental Triggers That Activate the Disease
Many people carry the genes for celiac disease their entire lives without ever developing symptoms. Then something changes. Researchers have identified several environmental triggers that appear to activate the disease in genetically susceptible people.
Viral infections are one of the most studied triggers. Infections with rotavirus, adenovirus, enterovirus, and hepatitis C virus are all associated with increased rates of celiac disease. A prospective study following at-risk children found that those infected with rotavirus were nearly twice as likely to develop celiac disease, and children who had two or more rotavirus infections had almost four times the risk. Another virus in the same family, called reovirus, has drawn particular attention: people with celiac disease have higher levels of reovirus antibodies in their blood compared to people without the disease. In animal studies, reovirus infection prevented the immune system from developing normal tolerance to gluten, essentially priming it to react aggressively instead.
Stressful life events also appear to play a role. In one study comparing 186 adults with celiac disease to 96 controls, 67% of celiac patients reported significant life events in the years before their diagnosis, compared to 38% of controls. The most common events were serious health problems and personal losses. Among women, 20% of those with celiac disease described a pregnancy as a triggering stressful event, while none of the women in the control group did. Stress may worsen the disease through two pathways: it can push someone with mild, unnoticed symptoms to finally seek medical attention, and it may also directly influence the immune response in people who are already genetically primed.
Why Some People Develop It Later in Life
Celiac disease is not just a childhood condition. While it can appear at any age, many people are diagnosed in their 30s, 40s, or later, often after a triggering event like surgery, pregnancy, or a severe gastrointestinal infection. The genes were always there, and gluten was always in the diet, but the immune system’s tolerance to gluten can break down at any point in life. This is why people sometimes say they “suddenly” became gluten intolerant after years of eating wheat with no problems.
Does When Babies Eat Gluten Matter?
For years, parents of at-risk children were told that the timing of gluten introduction could prevent celiac disease. The European Society for Pediatric Gastroenterology reviewed the evidence and concluded that gluten can be introduced anytime between 4 and 12 months of age without changing the overall risk. In high-risk children, introducing gluten earlier (at 4 or 6 months versus 12 months) led to earlier appearance of the disease, but by later childhood, the total number of children affected was the same regardless of when gluten was introduced.
One practical recommendation did emerge from the data: avoid giving large amounts of gluten during the first weeks after introduction and throughout infancy. While the timing doesn’t seem to change whether a child develops celiac disease, the quantity of gluten consumed early on may influence risk.
Putting It All Together
Celiac disease requires three ingredients: the right genes, gluten in the diet, and a trigger that breaks the immune system’s tolerance. You inherit the genetic susceptibility from your parents, you encounter gluten through everyday foods, and at some point, something tips the balance. That trigger might be a viral infection in childhood, a stressful period in adulthood, or something researchers haven’t yet pinpointed. Not everyone with the genes and the triggers will develop the disease, and not everyone who develops it will do so at the same age or with the same severity. But because the genetic component is so central, anyone with a first-degree relative who has celiac disease should be aware of their elevated risk, particularly if they develop unexplained digestive symptoms, iron-deficiency anemia, or bone density problems.