Although food allergies that trigger sinusitis are relatively rare, they do occur often enough that I'm always on the lookout for them in people whose symptoms cannot be explained by more common causes. The tip-off that such an allergy may be present is when postnasal drip is the primary symptom. If you are particularly bothered by such drainage—or constant collection of phlegm in the back of the throat, especially upon awakening— you may well have a food allergy and not even be aware of it.
What causes food allergies is not well understood, but it's clear that when certain people eat specific foods, undesirable reactions occur. In some cases, such as allergies to shellfish or peanuts, these effects can be immediate, resulting in hives or swelling of the face or throat. In severe cases, these allergic reactions can be life-threatening.
In most cases, however, the effects are more subtle. Symptoms have a gradual onset and are less marked, to the point where people often do not make the connection between the food and the subsequent reaction it causes.
Milk and wheat are the two foods that most commonly cause the allergic reaction that leads to excess mucus production and troublesome postnasal drip. This drainage can also block the nose, impairing breathing and blocking the sinus ostia, prompting an infection.
Diagnosing food allergies can be a bit tricky, as there is no standardized approach used by all allergists and test results can be unreliable. Some favor skin testing similar to that used to detect pollen and dust allergies; minute amounts of the food are placed just beneath the skin to see if any reaction occurs. Others use a blood test called RAST to look for antibodies to food proteins in the blood.
The best way to determine if you have such an allergy is an elimination diet; in other words, you stop eating the suspect food for a period of time and see if that makes a difference. I recommend a trial of at least two weeks, and four weeks is ideal—if you can hold out that long, then you'll know with some certainty whether you're really allergic.
During the trial, you have to be very strict in your diet. With milk, you need to cut out not just the milk you drink, but all products containing even small quantities of milk. That includes cheese, yogurt, and many baked goods. You'd be surprised at how many products contain small amounts of milk, including many breads, sauces, and salad dressings. You'll have to check labels to be sure products are milk-free.
One final milk note. It's the protein component in the milk, not the fat, that causes the increase in mucus production. So simply switching to nonfat milk, while perhaps good for your heart and waistline, won't affect mucus production.
With wheat and wheat-based products, such as bread and pasta, the source of the problem is also a protein—in this case, one called gluten. Again, eliminating wheat for two to four weeks should reveal whether you have this allergy.
People with sinus problems who truly are allergic to milk or wheat often see dramatic symptom improvement when they eliminate the offending food. Many of my patients whose postnasal drip did not improve with conventional medications (including antihistamines, steroid sprays, and antibiotics) have reported a huge decrease in the amount of mucus produced by their nose within a few weeks of starting an elimination diet.
While milk and wheat can worsen sinus symptoms, certain spicy foods may actually reduce them (see the sidebar "Hot Peppers, Anyone?").
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