A recent New York Times article tells us that what many people call food allergies are actually simple intolerances, and that allergies are being dangerously overdiagnosed. What is a true food allergy, and what can be done to fix them besides banning peanuts from schools and avoiding foods that make us itchy?
Allergies are caused by an inappropriate immune response to common things in the environment. Usually the offending allergen is a protein that comes from plants or animals like pollen or dander. Instead of the immune system recognizing that these proteins are harmless, it instead activates a crazy inflammatory response, causing the symptoms we recognize: itchy, runny nose, sneezing, rashes, and in some extreme cases, anaphylaxis.
This immune response is activated when antibodies bind to and recognize the globby 3D shapes of offending proteins, either proteins on the surface of dangerous pathogens or harmless allergens. Because 3D protein shapes can be similar even when proteins have different functions, sometimes allergic responses can be activated in response to a wide array of proteins. My food allergies, for example, are caused by a small group of proteins that is present in fruits and vegetables that have similar 3D shapes to the tree pollens that give me seasonal allergies. A large percentage of people allergic to birch trees like me also have allergic reactions to fruits like peaches, cherries, and strawberries, vegetables like carrots and celery, and nuts like almonds. But because the 3D shape of the protein is important in activating the allergy, I don’t get itchy when these foods are cooked, because high heat changes the shape of food proteins.
Even factoring in the fact of overdiagnosis, food allergies are on the rise in developed countries, with rates of serious allergy soaring just in the past few years. This change is now frequently attributed to the fact that many of us in developed countries are just too clean, leaving our immune system with nothing to do except get itself all worked up for no good reason. In places around the world where dirt and parasites are a more common part of childhood, there is very little incidence of serious allergies. This hygiene hypothesis says that if our immune system was challenged with more kinds of dirt and bacteria when we were younger, or was more distracted trying to keep us healthy, that allergies would just go away. There is of course a lot of good that comes from not growing up with unmanageable parasites and high rates of potentially deadly infectious disease, but perhaps there can be a happy medium between good health and a good immune systems.
This question is explored in a fascinating episode of RadioLab from last year all about parasites. In that episode we learn about a man with terrible allergies and asthma who gave himself a hookworm infection that basically cured him. I won’t go into the gory details of how he got hookworm, you should listen to the episode not close to any mealtimes for that, but the result is fascinating. By distracting his immune system with a harmless levels of an intestinal parasite, he was able to go outside again without having a life-threatening allergic reaction.
I’ve wanted my own hookworms ever since, although I prefer to wait until I can have medical supervision. I thought that opportunity had arrived on Sunday when the ads for the evening news after Lost included a story of researchers right here at two of the Harvard hospitals beginning a trial of hookworm infection as a cure for food allergy! I called the researchers hoping to sign myself up as a volunteer, but I’m sadly going to have to wait a few years it seems until they expand the study beyond just looking at peanut allergy (thanks for nothing FDA!).
In the meantime, I’m hoping to take another path to being able to eat some of the fruits and vegetables that I’m allergic to–genetically modifying the plants to delete the proteins that cause my allergy. The safety of genetically modified food is a serious and ongoing concern, but what if the genetic modification was meant to make the food safer in the first place? Many of the proteins that cause allergies are not required by the plant for survival, and the genes that encode them can be deleted or knocked down through several different methods, without adding any genes from other organisms or significantly changing the plant biology. Such plants would grow normally but would be hypoallergenic, safe to eat by everyone. This is one of the projects my iGEM team is working on, part of a potential future toolkit to custom-engineer the plants in your garden. Plants grow slowly and are hard to work with in the lab, so maybe it’ll also be many years before I can grow my own hypoallergenic strawberries, but I’m hopeful for an allergy-free future!