Science Questions

I’m interested in the mosquitoes thing because I’m obviously not very tasty to them but my wife is. We can spend the same sort of time out in the garden and I’ll come in without a bite and she’s absolutely covered. The other thing is that hers always come up much larger than mine and they last a lot longer. Within two or three days mine have gone and hers are just getting into their stride. They’ll be there for about a week or so. I just wondered if there’s any link known between the two things. Richard, Sawston

It’s all down to an immune response. People think that when you react it’s something that the mosquito’s done to you: a bit like a sting. That’s not the case. It’s in fact what your immune systems doing that’s making the mosquito’s bite unpleasant. It’s only the females because they need the blood when they want to lay eggs, they need a high protein meal: that means you. When a mosquito bites you what it does is to insert the proboscis, their mouth parts, into the skin and they probe around until they find a blood vessel. Usually a capillary which they get into and then they can start drawing blood. To stop the blood from clotting and also to ward off your immune system while they’re doing that they inject a cocktail of about 20 proteins that go into the local tissue. They keep the mosquito having a nice dinner without harm coming to it and it also means you don’t know it’s there, immunologically speaking. The problem is that it leaves the vestiges of its saliva in the wound site. This means that when the mosquito’s flown away your immune system flocks in and begins to react to it. It’s reacting to that foreign protein and that means as you get more bites over your lifetime you get better and better at responding. That means some people get quite vigorous reactions to mosquitoes; other people the immune system tends to damp down its effect. It’s a bit like having injections to damp down allergies, for example. It just depends on how your immune system is rigged up and some people have a form of their immune system that means they react more and more vigorously, sometimes until it gets really quite severe as James was saying earlier. In other people it tends to become less severe. Maybe you’re of the latter type and your wife is of the former. I hope that answers your question.

May 2008