May is Allergy Awareness Month: The Difference Between Allergies and Intolerances

 By Timothy Prentiss
Staff Writer
Kirkman Group, Inc.


For decades the rate of allergies has been rising. Media coverage and general awareness of the subject have likewise risen.

Clearly there are benefits to this growing awareness: restaurants are more likely to offer meal options for those with dietary sensitivities, such as gluten; schools are more likely to be more careful or prohibit foods that could cause allergic reactions, such as peanuts and more.

However, the increased attention given to allergies has led to a number of misconceptions. For example, according to an article on the website, WebMD, the number of Americans with food allergies has increased to the point where it’s somewhere between three and four percent; however, the number of people who believe that they have an allergy is nearly 15 percent.1 Put another way, about 10 percent of Americans believe they have an affliction they don’t actually have.

The prevalence of these misconceptions is likely caused, in part, by confusion with intolerances (also know as food sensitivities). Strictly speaking, an allergy causes an immune system response. If this response is sufficiently drastic, it can cause anaphylaxis, a potentially fatal condition during which a person’s blood pressure drops and their airways become blocked.

Unlike allergies, in the case of intolerances, the digestive rather than the immune system has an adverse reaction. For example, a particular food causes irritation in the stomach or intestines; or, the body lacks the enzymes to properly digest food, which can lead to bloating, cramps, diarrhea or other symptoms. Though possibly very uncomfortable, an intolerance reaction (unlike a true allergic reaction) will not be life-threatening.

It’s not just among lay people that there’s confusion about allergies. Even by the standards of medical research, where conclusions and best practices are constantly evolving, the subject of allergies seems particularly murky and full of contradictions. To avoid developing allergies, some medical researchers and physicians, suggest avoiding common allergens, however, others say that we should be exposing ourselves to common allergens, particularly at an early age.2 This illustrates that at the most basic level, there is no consensus about what causes allergies, or, in other words, what allergies are.

The dominant theory holds that allergic reactions are simply a sort of glitch, a dangerous overreaction on the part of the immune system to a non-threat. The immune reaction developed as a defense against parasitic worms (known as “helminths”) that historically were common residents of human intestines. Modern sanitation has left us relatively worm-free, consequently, IgE antibodies that in the past kept these worms in check will mount attacks against harmless proteins that bear similarities to helminth proteins. This explanation for the cause of allergies has led to “worm therapy,” in which parasitic worms are intentionally introduced to the bodies of allergy sufferers. This method has shown some promise.

Recently, a researcher at the Yale School of Medicine has been testing an alternate hypothesis. Ruslan Medzhitov believes allergic reactions are not simply dangerous overreactions to harmless substances. Rather, he believes allergens themselves can cause cellular damage; the allergic response (though dangerous) actually performs a protective role.3 

Clarifying the cause or, if Medzhitov is correct, the purpose of allergic reactions will no doubt lead to refinements in treatment methods. More importantly, there may eventually be an explanation for the continuously increasing number of allergy sufferers.


1. WebMD, Allergy statistics and facts. Accessed 5/24/16 from:
2. Chin, B., Chan, E., Goldman, R. MD Early exposure to food and food allergy in children. Canadian Family Physician. Accessed 5/25/2016 from:
3. Zimmer, Carl, Why do we have allergies. Accessed 5/24/16 from:
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