This question originally appeared on Quora. 
Answer by Rich Pollack, Public Health Entomologist
Each person (and other animal) exudes a cocktail of carbon dioxide and other emanations, and we also emit heat. Mosquitoes may discern any of us as human beings, but some of us will have a more attractive signature than others. You can line up 10 people and have each place one arm in a cage containing hundreds of mosquitoes. A few arms will quickly resemble a shag rug because of all the mosquitoes that have landed to feed. Yet others will have just a few mosquitoes in temporary residence, and a few arms will be nearly untouched. To further complicate matters, a person who is highly attractive to females of one kind of mosquito may not necessarily be as attractive to mosquitoes of other species.
Folks often ask whether they should befriend someone who is more -- or less -- attractive (to mosquitoes). The notion is that sitting next to a person who is more mosquito-attractive will somehow protect you by diverting mosquitoes from you to him/her. Genius, but the two of you together may draw in even more mosquitoes, and you may suffer even more bites than if you were a lone soul on the park bench. Ah, but what about sitting next to a mosquito-repellent person? That still may not benefit you. Certain emanations of that person may draw in mosquitoes from afar, but they then might home in on you once they were close.
With all this said, there is the concept of zooprophylaxis. Maintaining chickens, goats, or other animals in your home can, in some cases, divert bites by mosquitoes that would otherwise have been directed to a person. This can afford some limited protection against malaria and other mosquito-borne infections. Whereas this may offer a strategy for folks who live in primitive dwellings in rural regions and don't have resources to protect themselves by way of improved housing, pesticides, etc, it would not likely be embraced by travelers. Imagine checking in your hotel and finding a complimentary chicken in the room. Ah, but if it was a rooster, you'd not need to set the alarm clock.