Thursday, March 5th 2009

By mohini bhavsar

The upcoming month of April is relentless for allergy sufferers. Spring means sneezing bouts, nasal congestion, runny noses, red and itchy eyes, and for many, wheezing. One word easily summarizes the state of those affected: miserable. It’s time to bust out those anti-histamines, if you do not want to spend the entire spring and summer indoors. 

Allergies have been defined as a disorder of the immune system, commonly caused by environmental substances, called allergens. Common allergens include dust mite excretion, plant pollen or pet dander. Others examples include wool, drugs such as penicillin or local anesthetics, and even foods or insect stings. Allergies are caused by an excessive activation of white blood cells and triggers type 1 immediate hypersensitivity, which causes an extreme inflammatory response. Common allergic responses include eczema, hives, hay fever, and asthma. 

The Hygiene Hypothesis is a popular explanation for the recent rise in allergies. First proposed by David P. Strachan, the hygiene hypothesis suggests that the rising incidence of asthma, among other allergy-related diseases, may be a result of our health-conscious lifestyle and environmental changes. Perhaps we’re too clean for our own good? It argues that increased hygiene and lack of exposure to various microorganisms may be affecting our immune system so that we’re losing the ability to fight off certain diseases naturally. Autoimmune diseases, diseases that result from activation of the immune system, are increasing. The essence of the hypothesis is that the more hygienic we become, the more susceptible we are to autoimmune diseases. 

By killing off microbes and parasites that we encountered in the past, we may have thrown our immune system off balance. Supporters of the hygiene hypothesis believe that our immune system is now easily attacked and over stimulated by natural allergens that used to be harmless. Strachan believes that allergic diseases are caused by inappropriate immunological responses to harmless antigens. Can allergies be explained as an unintended consequence of striving to live longer and better?

Allergies are somewhat of a scientific puzzle, and explanations for the rise in allergies are debated. Nevertheless, maybe there is some truth in the hygiene hypothesis. It’s like trying to build muscles. You can’t really build muscles without first tearing them through exercise. Perhaps we need to stop being a super-clean, germ-free civilization and embrace nature for all that it is worth.

The hygiene hypothesis is not the only explanation in literature, although it’s the most popular one. Some researchers suggest that environmental factors such as toxins and chemicals may also play a role. As a result, the rise in allergies and associated diseases has been taken up by environmentalists in anti-pollution campaigns. These groups blame genetically modified foods, increased levels of carbon dioxide and rising temperatures. Also speculated is how a pregnant woman’s diet or breastfeeding may contribute to the development of a baby’s immune system. 

Either way, both explanations see allergies as the “disease of civilization,” the physiological response to an increasingly modern lifestyle. After all, autoimmune diseases and allergies are on the rise nearly everywhere in the developed world. Furthermore, it is not completely elucidated how chlorinated water, cleaner air, modern sanitation, improved personal hygiene and a reduction in microbial exposure has impact on immunity. 

Research studies show that children from larger families and those that have grown up on farms tend to have fewer allergies than one-child families in urban settings. More siblings means higher contact with microorganisms and a chance to build immunity. So is this an invitation to let kids be kids? Maybe, but allowing your kids to eat dirt is likely taking things too far.

Interestingly, there are a lot of allergy-proofing guidelines online, but many of them seem quite outlandish.  When are we being cautious for the sake of safety, and at what point are we over-doing it?

Despite all these questions, almost all scientists agree that the use of the word “hygiene” in the hypothesis theory is misleading. Cleanliness is important, and personal hygiene should not be abandoned. It has been suggested that the hygiene hypothesis be re-named to the “microbial exposure hypothesis” to avoid ditching sanitary practices. There’s no silver bullet for this one… the increase in allergies is a complex puzzle.