Why do mosquito bites merely itch while bee stings are painful?
Dear Straight Dope:
I've always liked the great outdoors, camping, boating, etc., but hate mosquitos bites just like everyone else. Although I've thought of blowing them up by flexing my muscles, let's say I have better things to do. What I'd like to know is why the bite is itchy and not painful. Other stinging insects such as bees and black flies hurt like hell.
SDStaff Doug and SDStaff Jill reply:
The mosquito's goal is to take something out, namely your blood. Mosquitoes are trying to bite without you noticing until it's too late. The itch you experience is just an aftereffect caused by your body's immune response.
The bee sticks something in — poison — to purposely make it hurt. Bees want you to feel pain, immediately. Entirely different chemicals are used. Black flies don't hurt their normal hosts the way they do humans, and if they do, it's a host that can't effectively kill a fly, so in that case it's more a matter of a bad match — they rarely bite a human and escape before being swatted.
A mosquito doesn't "bite" you, of course. Its proboscis works like a syringe to draw out blood. (Females are the culprits in this case; the males only feed on the nectar of flowers.) Some saliva is injected but the purpose is not to piss you off. It contains, among other things, an anticoagulant so your blood will pass easily through the mosquito's proboscis and digestive tract without clotting up like a milkshake.
The itchiness is not caused directly by the piercing proboscis or the chemicals in the mosquito spit but by the body's immune response to them. Your immune system releases histamine, a protein involved in many allergic reactions, in order to fight off a foreign substance. The histamine causes swelling around the puncture wound as blood rushes to the affected area, and as a side effect makes you itch. The histamine response speeds healing, so taking antihistamine drugs for relief of symptoms caused by mosquito bites is not necessarily a good idea. (Antihistamines are also commonly taken to neutralize inappropriate allergic reactions to substances that don't pose a danger to us, such as pollen.)
In many parts of the world, itchiness is the least of the problems caused by mosquito bites. Specific subspecies of mosquitoes are capable of transmitting serious diseases such as malaria (a major world killer, responsible for over 1.5 million deaths a year, mostly in tropical Africa), yellow fever, dengue, and several kinds of encephalitis.
Regarding flexing your muscle to trap and explode mosquitoes, save yourself the effort. We on the Straight Dope Science Advisory Board, again sacrificing ourselves for the good of the Teeming Millions, already tried it (If you flex your muscle when a mosquito bites you, will it swell up and explode?). Regardless of Lileth's insistent lies and perpetuation of an obvious myth in this Straight Dope column, trust me — it doesn't work.