Gluten and wheat: Sensitivity, allergy or celiac disease?

People who react sensitively to cereals such as wheat and rye often have digestive problems like diarrhea, constipation, cramping abdominal pain, and flatulence (gas). They might be tired and have headaches, too. These symptoms develop within hours or days of eating.

If you have a wheat sensitivity, you do not need to completely cut gluten and wheat out of your diet. In fact, doing so can have side effects. For instance, specially manufactured gluten-free products often have more calories and less fiber in them than gluten-containing alternatives do. People who have already cut this cereal out of their diet can gradually start to eat it again and then see how much they can tolerate.

An untreated wheat sensitivity is not known to have any serious short-term or long-term effects.

If you suspect you might have a wheat sensitivity, it is important to first rule out celiac disease or an allergy (see below). Your doctor will first ask you about your symptoms and eating habits.

A food diary can help you to find out which symptoms you experience, when, after eating certain foods.

The effects of a wheat allergy can already become noticeable within minutes or hours of eating. Babies and children usually react with typical allergy symptoms such as:

• Itching, a skin rash and swelling
• A hoarse voice, difficulty breathing and a runny or blocked nose
• Cramping abdominal pain, diarrhea and vomiting
• A racing heart (palpitations), drop in blood pressure, and even anaphylactic shock (anaphylaxis)
• Headaches

Wheat allergies are less common in adults. Adults usually have a reaction in their digestive organs (such as severe pain and vomiting) after certain additional triggers, such as physical exertion.

Your doctor will first ask you about your symptoms and eating habits. Keeping a "food and symptom" diary can help you to find out what may be triggering the reactions. Skin and blood tests can help to make a diagnosis. If all the signs are pointing towards a wheat allergy, a "gluten challenge test" can be done. This involves swallowing a substance containing gluten extracts.

Overall, wheat allergies are rare and less common in adults than in children. Unlike celiac disease, wheat allergies can go away again if you follow a strict wheat-free diet for several years. In particular, children who develop an allergy early on often have no problems with wheat anymore by the time they start school or become teenagers. To find out if the allergy is still there, their allergist or pediatrician can do the skin tests, blood tests and challenge test again.

Celiac disease can cause a wide variety of digestive problems, loss of appetite, tiredness and mood changes, and sometimes skin problems as well. But some people don't have any noticeable symptoms. You can read more about the possible symptoms of celiac disease here.

Your doctor will first ask you about your symptoms, whether you have gluten in your diet, and if so, how much. If the doctor suspects that you have celiac disease, they will take a blood sample to see if it contains (IgA) antibodies against an enzyme in the body called tissue transglutaminase (tTG or TG2). Very high levels are a clear sign of celiac disease.

The blood is also tested to see if there's an overall lack of immunoglobulin A (IgA) antibodies. In that case, the tTG-IgA antibody level will be low even if you have celiac disease, and further blood tests are needed. For all of these tests, a blood sample is taken at your doctor’s practice and sent to a laboratory to be examined.

For the test results to be reliable, you need to have enough gluten in your diet beforehand. 10 g of gluten per day are enough here, spread across 1 to 2 (or preferably 3 to 4) meals containing gluten. That may include bread, baked goods, pasta, or other foods with gluten in them. 100 g of dry pasta or white bread rolls contain about 9 g of gluten, and two slices of white bread weighing a total of 80 g contain about 5 g of gluten.

People who have already reduced the amount of gluten they eat have to increase it again for at least 3 months before the test. If severe symptoms occur during that time, the tests can be done sooner.

You can find further information about the various blood and gene tests, as well as the immune system reactions in the intestine, on the website celiacfacts-onlinecourses.eu.

If the blood test shows signs of celiac disease, tissue samples are taken from the upper small intestine during a gastroscopy. In this procedure, a thin tube with a tiny camera is inserted through your mouth and stomach. If the celiac disease has been around for a long time, there is often clear damage to the mucous membrane lining the intestine and to the tissue directly beneath it. The level of damage to the crypts and villi is generally assessed using the Marsh classification system.

There are 6 Marsh types, ranging from type 0 (normal) to types 3a, 3b and 3c (from minor to most severe damage). Types 3a to 3c mean there is clear damage.

If you have Marsh type 1, the lining of your intestine is inflamed but not damaged. You still might have celiac disease, though. To find out, the Marsh type is always considered together with the blood test results and any symptoms. Minor damage to the lining of the intestine can be caused by other things, such as food allergies or an imbalance of bacteria in the intestine.

Celiac disease can be diagnosed without taking tissue samples if

• gastroscopy isn't possible, and the
• blood test results clearly point to celiac disease.

Children and adults with a higher risk of celiac disease can be tested even if they don’t have any noticeable symptoms. Those at higher risk include people with

• children or parents who have celiac disease, or with siblings or grandparents who have the disease,
• certain genetic conditions (like Down syndrome, Turner syndrome or an IgA deficiency), and
• other autoimmune diseases (like type 1 diabetes, autoimmune hepatitis, Hashimoto’s disease or rheumatoid arthritis).

People with an increased risk can also have their blood tested for antibodies against an enzyme in the body called tissue transglutaminase (tTG).

On top of that, they can have a gene test to look for certain gene types that increase the risk of celiac disease, known as HLA DQ2 and DQ8: If those gene types are not found, celiac disease can be ruled out. But even if you do have these gene types, it doesn't necessarily mean you have celiac disease. Unlike blood tests for antibodies, this gene test can be done if you're following a gluten-free diet and regardless of whether you have symptoms.

If the blood tests cannot rule out celiac disease, a tissue sample can provide clarity: The mucous membrane lining the intestine might still have been damaged even if you don't have symptoms.

The diagnosis of celiac disease is similar in children and adults. But there is no need to do a gastroscopy in children and teenagers under the age of 18 if the concentration of tTG antibodies in their blood is ten times higher than the upper limit. Parents can discuss the pros and cons of gastroscopy with a specialist for pediatric gastroenterology.