Celiac disease is caused by an abnormal immune reaction to gluten, a protein found in wheat, barley, and rye. But gluten alone isn’t enough to trigger the disease. It takes a specific genetic setup, an immune system that misidentifies gluten as a threat, and likely one or more environmental factors to set the whole process in motion. About 1% of the global population has celiac disease, though rates vary by region, from roughly 1 in 133 people in the United States to 1 in 66 in Sweden.
Genetics Set the Stage
Celiac disease cannot develop without a particular set of immune system genes. More than 90% of people with celiac disease carry a gene variant called HLA-DQ2, and most of the remaining cases carry HLA-DQ8. These genes code for proteins on the surface of immune cells that present fragments of food to the rest of the immune system. In people with these variants, the proteins are shaped in a way that makes them especially good at latching onto pieces of gluten and flagging them as dangerous.
Here’s the important nuance: carrying these genes doesn’t mean you’ll get celiac disease. Between 30% and 40% of the general population has HLA-DQ2 or HLA-DQ8, yet only about 3% of carriers ever develop the condition. That gap tells researchers that additional genetic and environmental factors are required to push someone from “at risk” to “actively diseased.” Dozens of other gene variants have been identified that each contribute a small amount of additional risk, mostly related to immune regulation and intestinal barrier function.
How Gluten Triggers an Immune Attack
Gluten is unusually difficult for the human digestive system to break down. Unlike most food proteins, which get chopped into tiny, harmless fragments, gluten leaves behind large, partially digested pieces called gliadin peptides. In most people, these fragments pass through without incident. In someone with celiac disease, they set off a chain reaction.
The trouble starts when gliadin peptides cross the intestinal lining and encounter an enzyme called tissue transglutaminase, or tTG. This enzyme chemically modifies the gliadin fragments in a way that makes them bind tightly to the HLA-DQ2 or DQ8 proteins on immune cells. Once bound, those immune cells treat the modified gluten as a serious threat and launch an inflammatory response. The immune system releases signaling molecules that recruit more immune cells to the area, and those cells begin attacking the lining of the small intestine itself.
The damage concentrates on tiny finger-like projections called villi that line the small intestine and absorb nutrients from food. Over time, the villi flatten and shrink, a process called villous atrophy. This is what causes the hallmark problems of celiac disease: your small intestine progressively loses its ability to absorb nutrients from the food you eat. The body also produces antibodies against tTG itself, which is why blood tests for these antibodies are the primary screening tool for the disease.
The Role of a “Leaky” Gut Lining
For gliadin to reach the immune cells beneath the intestinal surface, it first has to get through the gut barrier. The cells lining your intestine are sealed together by structures called tight junctions, which control what passes between them. In celiac disease, these junctions become abnormally loose.
A protein called zonulin acts as a natural regulator of tight junction permeability. In people with celiac disease, gluten itself triggers increased zonulin release, which opens the junctions wider than normal. This allows more of those large, partially digested gliadin fragments to slip through the barrier and reach the immune system underneath. It creates a self-reinforcing cycle: gluten loosens the barrier, more gluten gets through, and the immune response intensifies.
Environmental Triggers That Tip the Balance
Since most people with the genetic risk never develop celiac disease, researchers have focused heavily on what environmental factors might flip the switch. Several have emerged as likely contributors.
Viral Infections
Gut infections, particularly from viruses that target the intestinal lining, have been linked to celiac disease onset. Rotavirus infections in early childhood are associated with increased celiac risk in genetically susceptible children. The leading theory is that a viral infection can temporarily damage the intestinal barrier, allowing gliadin to reach the immune system at a moment when the immune environment is already inflamed and primed to overreact. Researchers at the University of Chicago have noted that if specific viral infections are confirmed as strong triggers, early vaccination against intestinal viruses like rotavirus could potentially reduce celiac incidence in at-risk populations.
Gut Bacteria Imbalances
The mix of bacteria living in the gut also appears to play a role. Research published in the Proceedings of the National Academy of Sciences found that children who go on to develop celiac disease show shifts in their gut bacteria before the disease appears. Specifically, they have fewer bacteria that produce a compound called butyrate, which helps maintain the intestinal lining and calm inflammation. They also tend to have lower levels of beneficial Bifidobacteria and higher levels of pro-inflammatory bacterial species. Whether these imbalances are a cause or an early consequence of the disease process is still being worked out, but the pattern is consistent across multiple studies.
Gluten Introduction in Infancy
Parents of at-risk children often wonder whether the timing of a baby’s first exposure to gluten matters. European pediatric guidelines reviewed the evidence extensively and concluded that introducing gluten anywhere between 4 and 12 months of age does not appear to change a child’s overall risk of developing celiac disease. Breastfeeding during gluten introduction, once thought to be protective, also does not reduce the risk. The one practical recommendation: avoid giving large amounts of gluten in the first weeks after introduction, though the evidence behind even this advice is limited. In short, you can’t prevent celiac disease by carefully timing when gluten enters your child’s diet.
Why Many Cases Go Undetected
Celiac disease has a reputation as a digestive condition, with symptoms like bloating, diarrhea, and abdominal pain. But a significant number of people with confirmed intestinal damage have no gut symptoms at all. Among first-degree relatives of celiac patients who were screened and found to have the disease by biopsy, 34% were completely asymptomatic. This “silent” form of celiac disease is one reason the condition is heavily underdiagnosed.
When symptoms do appear, they aren’t limited to the gut. The immune-driven inflammation and nutrient malabsorption can show up as iron deficiency anemia, bone thinning, skin rashes, fatigue, nerve tingling, or unexplained weight loss. Some people are diagnosed only after developing one of these complications rather than classic digestive symptoms. Children in particular may present with poor growth or delayed puberty rather than stomach problems.
What Happens Without Treatment
Because the damage is driven by an ongoing immune reaction to gluten, the intestinal destruction continues as long as gluten remains in the diet. Over time, the consequences extend well beyond the gut. Chronic malabsorption can lead to significant bone loss, since the intestine can’t properly absorb calcium and vitamin D. Nerve damage from nutrient deficiencies can cause numbness and coordination problems. Skin conditions, lactose intolerance, and fertility problems are all documented complications.
Some of these consequences are reversible once gluten is removed and the intestinal lining heals, which typically takes months to years on a strict gluten-free diet. Others, including severe bone loss and certain forms of infertility, may not fully recover. The only current treatment for celiac disease is lifelong, complete avoidance of gluten. Even small, repeated exposures can sustain the immune reaction and prevent the intestine from healing.
Family Risk and Screening
Because celiac disease is so strongly genetic, it clusters in families. First-degree relatives (parents, siblings, and children of someone with celiac disease) have a substantially higher risk than the general population, and siblings and daughters appear to be at particularly elevated risk. Given that more than a third of affected relatives may have no symptoms, screening with a blood test for tissue transglutaminase antibodies is recommended for close family members. In children, antibody levels 10 times the normal upper limit, confirmed by a second type of antibody test, can be enough to establish a diagnosis without a biopsy.