Maybe we need a greater exposure to worms. Yup, worms. As well as other assorted parasites. At least that’s what some researchers are thinking as they look into the increasing incidence of allergies. An allergy is basically a mistake made by the immune system. Instead of targeting disease-causing microbes, immune cells unleash their chemical weaponry against a substance they mistakenly perceive to be harmful. That innocent bystander may be found in pollen, in food or in various consumer items ranging from jewelry to fabrics. Why does this happen? And why is it happening with greater frequency, particularly in the western world? The rapid rise in allergies and their particular geographic distribution suggest that environmental factors are at play.
Maybe, as some suggest, our early life is just too clean. Children are not exposed to as many bacteria and viruses as in the past, and as a result, their immune system doesn’t get the training it needs to battle these invaders. Instead, the immature immune system responds to some harmless substance and attempts to expel it by triggering sneezing, coughing and tearing. All this makes for an intriguing little story, but is there any evidence to support it? Perhaps surprisingly, there is.
The first clue is that in countries where infection by parasitic worms is common, the incidence of allergies is low, but rises when children are treated for parasites. A study of more than 2800 school children in Ecuador showed that allergies were less prevalent among those infected with worms, and a study in Gabon indicated an increase in allergies among children treated with a worm-killing medication. It is as if these parasites somehow manage to tune down the immune system to prevent themselves from being expelled, and this modulation of immune activity also reduces the chance of reaction against other substances.
Obviously there is great interest in any substance the parasites may release to allow the immune system to tolerate them. Researchers at the University of Strathclyde in Scotland have taken the first step towards unraveling this mystery by showing that, at least in the laboratory, extracts of worms can disarm mast cells, a type of white blood cell that initiates an allergic reaction through the release of histamine. The hope is that in the future some sort of worm extract can be used to trick the immune system into reacting as if it were accommodating a parasite.