Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Cross-Contact During Food Preparation May Trigger Allergies

Dear Doctor: My boyfriend wants to take me to his favorite Thai restaurant, but I'm a little worried; Thai cuisine uses a lot of peanuts and I'm allergic. For people with food allergies, how dangerous is it to eat meals made with equipment also used to cook allergen-containing foods?

Dear Reader: Food allergies in the United States appear to be on the rise, which makes your question increasingly relevant. For individuals with allergies, even a tiny amount of the allergen can set off a reaction. This includes consuming food that doesn't actually contain the problem ingredient, but has been produced on equipment where the allergen is present in some form. This is known as cross-contact, and it can cause serious problems.

If you accidentally consume a food that your immune system has identified as dangerous, you're in for a physical reaction. This can be as mild and manageable as itchy skin, a headache or an upset stomach, or as severe as anaphylaxis, which can lead to death.

Although the steady uptick in allergies is worrisome, the newest research, which analyzed data from the medical records of 2.7 million patients, actually dials back the previous estimate of people with food allergies in the U.S. Instead of the widely quoted 5 percent, this study pegs the number at an average of 3.6 percent.

More women (4.2 percent) than men (2.9 percent) have food allergies. Asians had the highest incidence at 4.3 percent. Latinos had the lowest rates at 2.8 percent. Still, identifying and diagnosing a food allergy can be difficult, so all estimates are just that -- a researcher's best guess.

Your peanut allergy is in the top five of food reactions. Shellfish is first, followed by fruits or vegetables, dairy, then peanuts. Needless to say, the range of foods that can cause an allergic reaction is far more diverse.

To help people with allergies, the U.S. Department of Agriculture requires food labels to clearly identify the presence of any of the major food allergens. Also, if a product uses nuts, the specific nut must be named. But -- and this is important -- the "this product may contain" language on a food label, which warns of possible cross-contact, is voluntary. That means the absence of that warning doesn't necessarily eliminate the chance of cross-contact.

When it comes to dining out, where the preparation of your food is out of your control, your best defense is to be your own advocate. Call ahead to the restaurant and ask to speak to the chef or manager about your concerns. Ask for details about the precautions the restaurant takes to prevent any trace of an allergen from finding its way to your plate. (You'll get the most relaxed response when you call during off-peak hours.)

During spur-of-the-moment restaurant visits, enlist the aid of your server. Clearly explain what you're allergic to and how it may affect you, and ask him or her to let the kitchen know as well. Find out how the kitchen handles potential cross-contact. And, because we live in an imperfect world, please remember to always carry an EpiPen.

(Send your questions to, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)