And by "some people" I mean me. Why is it that an evening stroll leaves me feeling eaten alive while my companions are left blissfully un-bitten?
First of all, it's probably not all in my head (although it could be — most people are bad sources about their own mosquito attractiveness). Studies suggest that about 20 percent of people are "high attractor types" who are especially appealing to the female mosquitoes seeking out blood for the extra protein they need to lay eggs. Of course, not all mosquitoes are the same. There are 150 different species in the United States, each with their own blood-sucking proclivities. But since you probably won't know — or care — if the bugger biting you is Culex pipiens or Aedes aegypti, let's consider some of the more general properties that affect your mosquito appeal.
It's true, mosquitoes have discerning fashion taste. Or at least, they're more likely to spot you as a target if you stand out from your environment. Dark colors, especially, will attract more of the insect.
Similarly, the more you move, the easier you are to identify as a living, breathing, vessel full of delicious blood.
Visual clues allow the mosquito to locate you from relatively far away, but as she approaches, it's your body heat that draws her in. This puts pregnant women, who average about 1.26 degrees Fahrenheit warmer than others, at a particular risk — a fact which has been substantiated by a number of studies.
This is another reason pregnant women are at a disadvantage. Mosquitoes can detect carbon dioxide using a special organ called a maxillary palp from as far as 164 feet away. Since everyone emits CO2 simply by exhaling, it comes down to relative amounts. Unfortunately for mothers-to-be, pregnancy causes women to emit 21 percent more CO2. This is also why kids are often safe from bites, when bigger, more CO2-emitting adults are around.
On the flip side, pregnant women are (presumably) avoiding another mosquito attractor: alcohol. Although it's unclear how mosquitoes go about detecting the presence of ethanol, studies show that drinking even just 12 ounces of beer will significantly increase the attention you receive from the pests.
The Properties of Your Skin and Sweat
Up to 85 percent of your susceptibility to mosquito bites has nothing to do with what you're drinking or wearing — it's just genetic. Specifically, the composition of your skin bacteria — the kind that naturally and healthily exists there — can serve as an attractor. As can the levels of lactic acid, uric acid, ammonia, and other substances present in your sweat.
Another factor you can't control? Your blood type. And it stands to reason that, if the mosquito is there to suck your blood, she cares what kind she's getting. People with blood type O are more prone to mosquito bites than those with type B, with type A folks bringing up the rear.