ST. LOUIS — Rabia Rahman is as much a detective as a dietitian when she works with her patients to help them avoid gluten.

“I had one patient who got really sick from licking an envelope," said Rahman, who’s both a nutritional counselor and an instructor in the department of nutrition and dietetics at St. Louis University.

Ironically, gluten is used in the binders or coatings of some medications that patients may be taking to feel better. And many of Rahman’s female patients are surprised to find out that gluten is sometimes an ingredient in makeup and lipstick.

Helping patients eliminate gluten from their diets is easier than ferreting out some of these more obscure uses, but it still poses significant challenges.

“We’ll always go over food habits and cover the broad items like wheat, barley and rye, which means they shouldn’t eat regular cakes, breads and pastas," Rahman said. “But then I work with them to go over ingredient lists on labels closely and avoid specific items — hydrolized wheat starch, or anything that says malt, graham or spelt.

“There’s often gluten where you really don’t expect it. Soy sauce is a big one; broth soups, potato chips and even French fries, which are sometimes dipped in a starch to preserve them."

The medical reasons for going gluten-free, says Rahman, range from mild gluten intolerance to wheat allergies and celiac disease, an autoimmune disease in which consumption of gluten damages the small intestine. Blood tests can diagnose allergies and celiac disease, and Rahman calls a small-intestine biopsy the “gold standard" for diagnosis of celiac.

But there aren’t any specific tests for gluten sensitivity.

“That diagnosis often comes after a patient has gone from doctor to doctor to find out why they just don’t feel well," Rahman said. “Sometimes it’s (gastrointestinal) symptoms, but many times the symptoms are less obvious — tiredness, headache, or even sometimes depression."

Rahman has her patients keep a log of both their food consumption and their symptoms and eventually may recommend that they eliminate gluten from their diets. Or, in some cases, she may work the other way by having the patients go gluten-free to see if it makes their symptoms go away.

In either case, she says, adopting a gluten-free diet gets easier every year.

“Even in the past five years, there’s been a huge increase in cookbooks, in what’s available in stores and restaurants and in online support," Rahman said.

However, she adds, part of the demand has been generated by a certain trendiness in gluten-free lifestyles that’s been aided by their adoption by various celebrities.

“They’re using it as a fashion statement, or in some cases they’re saying it might help with weight loss," Rahman said. “But there’s no medical reason to follow it unless you have to."

But that said, she advises her patients and anyone else who’s been diagnosed as gluten-sensitive not to be shy about it.

“Eating out or at someone’s house are things that many patients find very, very difficult," Rahman said. It’s not just the food itself — there are issues of cross-contamination, as simple as crumbs left when regular bread is made in the same toaster."

“But you have to be willing to advocate for yourself," she added. “It’s also really important to involve family members and friends. You’ll often get a lot of support that really helps you stay on top of it."