Red flag: Persistent rash that you want to scratch raw
What it means: Dermatitis herpetiformis (DH) -- clusters of small, ferociously itchy blisters that show up repeatedly in the forearms near the elbows, the knees, the buttocks, the back, or the face or scalp -- are a hallmark of celiac disease, or an allergy to gluten. As many as one in four people with celiac disease have DH.
More clues: The rash appears on both sides of the body. Itching and burning are so intense you can hardly quit scratching. People with DH don't usually have the digestive symptoms of celiac disease, but they're intolerant of gluten just the same. DH often shows up between ages 30 and 40, and most often in people of northern European heritage.
What to do: Report the rashes to your regular doctor or a doctor who specializes in skin disorders to evaluate and rule out other causes. Blood tests and a biopsy of tissue from the small intestine are used to diagnose DH. A gluten-free diet for life is usually advised to keep symptoms at bay; this includes banishing foods, beverages, and medications that contain wheat, barley, rye, and sometimes oats. Drugs may help control the rashes.