In simple terms, from the Mayo Clinic:

Celiac (SEE-lee-ak) disease is a digestive condition triggered by consumption of the protein gluten, which is primarily found in bread, pasta, cookies, pizza crust and many other foods containing wheat, barley or rye. People with celiac disease who eat foods containing gluten experience an immune reaction in their small intestines, causing damage to the inner surface of the small intestine and an inability to absorb certain nutrients.

Celiac disease can cause abdominal pain and diarrhea. Eventually, the decreased absorption of nutrients (malabsorption) that occurs with celiac disease can cause vitamin deficiencies that deprive your brain, peripheral nervous system, bones, liver and other organs of vital nourishment.

No treatment can cure celiac disease. However, you can effectively manage celiac disease by changing your diet.

Symptoms:

There are no typical signs and symptoms of celiac disease. Most people with the disease have general complaints, such as:

• Intermittent diarrhea
• Abdominal pain
• Bloating

Sometimes people with celiac disease may have no gastrointestinal symptoms at all. Celiac disease symptoms can also mimic those of other conditions, such as irritable bowel syndrome, gastric ulcers, Crohn’s disease, parasite infections and anemia.

Celiac disease may also present itself in less obvious ways, including:

• Irritability or depression
• Anemia
• Stomach upset
• Joint pain
• Muscle cramps
• Skin rash
• Mouth sores
• Dental and bone disorders (such as osteoporosis)
• Tingling in the legs and feet (neuropathy)

Some indications of malabsorption of nutrients that may result from celiac disease include:

• Weight loss
• Diarrhea
• Abdominal cramps, gas and bloating
• General weakness and fatigue
• Foul-smelling or grayish stools that may be fatty or oily
• Stunted growth (in children)
• Osteoporosis