Summarize this article in one sentence.
Many physicians and allergy specialists can offer skin and blood tests to determine which foods may be causing your symptoms. Celiac disease results from an immune system reaction to gluten that is caused by the development of antibodies working to attack gluten like a foreign substance in the body. A biopsy of the small intestine can be collected and study to confirm whether gluten intolerance is caused by Celiac disease or a simple sensitivity. In individuals with Celiac disease, the villi (similar to small hairs lining the inner intestinal walls) are often damaged and matted under the magnification of a microscope lens. Visual inspection of the intestines can help identify whether the gluten sensitivity is caused by true Celiac disease or another condition. Because Celiac disease damages the small intestine’s villi, which absorb nutrients from food, individuals with the disease may suffer from vitamin deficiencies. Individuals with gluten intolerance do not necessarily have difficulty absorbing nutrients from other foods, unless the intolerance is actually caused by Celiac disease.

Summary:
Get an allergy test. Get a blood antibody test. Take a sample of the small intestine. Perform an endoscopy or camera pill swallow. Check for vitamin deficiencies.