Don't you just love the summer? The mere sight of something green and pollen filled is enough to reduce millions of us to snotty, sneezing, mucus-headed grotballs, unable to smell or taste all the lovely burnt barbecued food summer has to offer. Yup, hayfever brings joy to so many, and every year, more and more people suffer from this allergy to nature. And it's not just hayfever that is on the up. Allergies to dust, pets, food, and pretty much everything else are becoming more and more common, and the increase in asthma sufferers must be making the manufacturers of those little blue inhaler thingies very, very rich. So what is it with humans and our inability to cope with the world around us?
Today, we live particularly sterile lives and many people suggest that, rather than making us healthier, this is having the opposite effect and making us more prone to allergy. Basically, an allergic reaction (also known as Type I hypersensitivity) occurs when your immune system freaks out a bit and reacts to something that isn't actually trying to hurt us. If we are never exposed to any dirt as kids in past decades were (I used to eat mud so that could explain why I don't get the summer snots as much as others), our immune system doesn't know what is normal and what is bad, and starts attacking bits of harmless pollen that we inhale. The runny nose and other nasty symptoms are our bodies trying to flush out the evil pollen that has dared to creep into our lungs and nose.
Its not just dirt that we have managed to eliminate from our lives over that last century or so. The thing is, humans have evolved alongside parasites and in the wild would have been infected with worms, lice and fleas for most of our lives. I know, you probably don't really like the idea of Mr Wiggly worm and his friends taking up residence in your intestines but, for thousands of years, humans have got on OK with these icky companions.
Recently, scientists have started suggesting that parasites can keep the immune system in balance. Our bodies can attack a threat with two types of immune response. A Th1 response is mounted to fight a bacterial invader while a Th2 response is thought to have evolved to fight parasites. Both of these responses are important parts of our immune system but, in the case of allergies, there is an imbalanced Th2 immune response. Parasites possess mechanisms for reducing the immune response against themselves enough to allow them to survive in the human host. So without exposure to intestinal worms and other parasites, the immune system is left unchecked and can over-react to environmental substances by mistake.
So why have humans worked so hard at ridding ourselves of these little invaders if they're actually a good thing? Well, in Third world countries where poor diet is a major problem, the evil side of parasites can be seen. In the West, we all eat enough to replace anything that intestinal worms take from our bodies but people in undeveloped countries lose more nutrients than they can replace through diet. For example, in countries where filarial worms were once very common, lots of people were dying of the parasite infections. So western doctors went in and treated them. Interestingly, when they got rid of the worms they started seeing an increase in those suffering from allergies.
Could parasites help us today in the west? After all, the harmful effects of intestinal worms can now easily be kept under control by diet and drug treatment. There is one UK scientist who accidentally infected himself with hookworm and found that his allergies completely disappeared. Rather than treating the infection, he decided to kept them. But then the worms ate him from the inside and he died? Well no, although many people imagine parasites to be the stuff of nightmare our scientist was just fine. He didn't experience any nasty effects and only knew he was infected by looked at his poo under a microscope and counting the eggs (how nice).
While most people would probably chose a touch of hayfever over
a worm infection, there are some sufferers of more serious allergic
conditions where parasites could really improve their lives. Ulcerative
colitis is an incurable condition when the immune system starts
to attack the lining of the colon. So a doctor decided to test
whether drinking a sports drink containing whipworm eggs could
help. The 6 patients involved in the trial all went into remission
from the disease and could live normal lives.
