By Dr. John Weiner
Surveys show that up to 70% of people with asthma believe that some foods can trigger exacerbations. But if you test BLINDFOLDED adults with disguised food, so that even the people running the test don’t know what’s in the food until the end of the test (so-called double-blind testing), less than 5% will get asthma. So the prevalence of food-induced asthma is actually quite low. But it can be important, and there is no doubt that a few people will get sudden and very severe asthma with certain foods.
There are three types of food allergy.
THE FIRST SORT IS DANGEROUS…
In this type, there is true, full-blown, immediate allergy to a certain food protein. Examples include those people who get swelling of the mouth and throat, often with hives or even collapse, to foods such as peanuts, other nuts, fish, shellfish, seeds such as sesame, or (usually in infants) milk or egg. Asthma may accompany these severe reactions. {Note: distinguishing fatal anaphylaxis from asthma at autopsy is often difficult.}
As readers of this website well know, avoiding food triggers is a basic precaution, and U.S. patients should carry epinephrine should be carried for inadvertent exposures, although the same medicine is called adrenaline everywhere else. If you have this type of life-threatening allergy, especially if you have asthma, speak to your doctor about getting assessed.
THE SECOND SORT IS SULFITE ALLERGY AND MIGHT BE DANGEROUS…
Sulfite (also called metabisulfite or additive 220 and similar numbers) is added to foods as a preservative. This one means a great deal to me personally because I make my own wine, but other foods that may contain this chemical include salad dressings, sauces, and dried fruits. Foods can contain sulfite should list it as an additive.
When you eat these foods, the sulfite (which has morphed into a gas called sulfur dioxide) is breathed in. Normally quite harmless in those concentrations, the sulfite may trigger wheezing, especially if the asthma is poorly controlled. The subsequent asthma attack can range from trivial to very serious.
If you still wheeze with this additive despite well-controlled asthma, then a full assessment is suggested. Speak to your doctor.
THE THIRD SORT IS VERY UNCOMMON AND OFTEN DIFFICULT TO PROVE…
Some people say that other food additives, such as colors, other preservatives, or MSG, cause their asthma. Others report that certain foods (such as yeast, wheat or dairy products) cause fatigue, rash, headache, or asthma, for example. These types of disorders are often called food intolerance. The prevalence of these disorders is very low.
In 1998, some colleagues and I performed the first double-blind study in the world on dairy and asthma, but could not demonstrate a definite link.[1] We were looking at food intolerance, NOT true sudden food allergy. (This is an important distinction, because the most severe respiratory symptoms of anaphylaxis result from reactions in already-inflamed lung tissue.) In real life, there are exceptions, but the association is very uncommon.
Also, in a rigorous study, also in 1998, we also failed to show that MSG triggered an asthma attack. Again, there are rare exceptions, but the perception is much higher than reality. There are no reliable blood, skin, urine, hair or machine tests for this type of allergy. The only reliable test is an avoidance diet followed by a scientific challenge (eating a specified quantity of the food). THIS SHOULD ONLY BE DONE UNDER MEDICAL SUPERVISION, AND SOMETIMES IT IS DONE IN HOSPITAL. Your local Chinese restaurant is not a suitable research venue.
WHAT TO DO?
The first step is to control your asthma. Remember that your asthma is out of control if you use a reliever/rescue puffer several times a week, or if you wake at night and need a reliever/rescue puffer. Swing into your action plan and see your doctor.
If you feel foods trigger your asthma, then please do not rely on unscientific tests for food allergy listed in my other post. These bizarre tests will overestimate your food intolerance whatever continent you are living in, and the only measurable effect will be weight loss in your bank account. Your asthma is too important for that, and also you will unnecessarily restrict your diet (or, more importantly, your child’s diet). Speak to your doctor.
[1] “Do dairy products induce bronchoconstriction in adults with asthma?” Rosalie K. Woods, MPH, APD, John M. Weiner, FRACP, FRCPA,b, Francis Thien, MD, FRACP, Michael Abramson, PhD, FRACP and E. Haydn Walters, DM, FRACP, FRCP, Melbourne, Australia Journal of Allergy and Clinical Immunology, January, 1998
[2] “The effects of monosodium glutamate in adults with asthma who perceive themselves to be monosodium glutamate–intolerant” Rosalie K. Woods, MPH, APD, John M. Weiner, FRACP, FRCPA,b, Francis Thien, MD, FRACP, Michael Abramson, PhD, FRACP and E. Haydn Walters, DM, FRACP, FRCP, Melbourne, Australia Journal of Allergy and Clinical Immunology, June 1998
Dr. John Weiner is an allergist and clinical immunologist in Melbourne, Australia. His website is AllergyNet Australia www.allergynet.com.au and he is active on Twitter @AllergyNet, where this piece was originally published. His first piece for us on the allergy problems encountered by U.S. servicemen in Australia remains one of my favorites. You can read it here.
Photograph by www.getfrank.co.nz