Is Better Hygiene Causing More Allergies?
If you follow the sitcom ‘The Big Bang Theory’, you would probably remember how Howard gobbled peanuts to hide his friend from a surprise birthday party, even though he was allergic. Though it was hilarious, allergies are a serious health issue!
Allergies are a growing concern, primarily in developed countries like the US. About 15 million Americans suffer from some form of food allergy. Twice as many children suffer from allergies than adults. Peanuts, milk, eggs, wheat, nuts, soybeans and shellfish account for a large majority of reported allergy cases. The situation is troublesome because these are common food ingredients, and even trace amounts can trigger anaphylaxis (a severe allergic reaction) that requires immediate medical attention.
Allergies are an over-reaction of the immune system, which keeps a cautious eye on anything that enters our body. As humans evolved, the immune system learned to tell apart foreign entities from our own. When the immune system detects foreign substances (called antigens), it secretes antibodies (also known as immunoglobulins) and triggers a cascade of chemical signals which sound the trumpet, initiating an immune system war against the invader.
Certain foods contain antigens which can trigger an immune reaction. However, we don’t generally develop a reaction against food antigens because of the regulatory immune cells which constantly sample food in the intestine and teach our bodies what is a red flag. This is usually effective, but when our regulatory immune cells aren’t working properly, we see an over-reaction against certain foods.
In some cases, there may be an unexpected cause of food allergies. One class of antibodies, IgEs, constitute our main line of defense against parasites like roundworms or flatworms, and interestingly, the biological structure of parasite antigens shares some similarities with that of food antigens. Sometimes IgEs get confused when they detect these similarities, and they start an allergy chemical cascade. The response varies from mild hay fever, vomiting, and diarrhea to severe anaphylaxis. Yet, parasites and food are very different — why would nature engineer us this way?
In developed parts of the world, our immune systems don’t get enough exposure to organisms like parasites due to better hygienic conditions. It is thought that the less the immune system responds to these kinds of pathogens, the more it will attack innocent proteins from food. Researchers call this the ‘hygiene hypothesis,’ which triggers allergies as well as autoimmune disorders (conditions where the immune system starts attacking cells in our own body).
The “hygiene hypothesis” might explain why the number of people with food-induced allergies is increasing over time. According to the CDC, food allergy prevalence increased 18% from 1997 to 2007 in children under 18. Unfortunately, few studies have examined the change in incidence of food allergies over time.. A comparison of allergies in developed and undeveloped countries might tell us more about whether different hygienic conditions are associated with food allergy.
As of now, there is no permanent cure for allergies, or the body’s confusion between parasitic and food antigens. Identification and avoidance of problem foods is the only way to go. Most allergy treatments are designed to combat the allergy attack. For instance, epinephrine (marketed under EpiPen®) is used in an emergency room scenario to treat anaphylaxis. Steroids, antihistamines, and asthma drugs are used to alleviate milder symptoms.
Finding a curative approach to the ‘hygiene hypothesis’ is not easy. For one, we can’t ethically limit sanitation standards, or start giving infectious agents to children or adults. However, a recent study found that Crohn’s disease was greatly alleviated by parasitic proteins that were given to the patients. Standardization and safety would be a primary concern for this kind of strategy. As more countries improve their health care, it looks like the prevalence of allergies is only going to intensify. Finding a better strategy is, therefore, crucial.
Edited by Kasia Grzebyk