Mosquitoes bite humans primarily because female mosquitoes need blood to produce eggs. They are attracted to us through a combination of cues: carbon dioxide from our breath, body heat, and especially skin odors made up of chemicals like lactic acid and carboxylic acids. Some people are more prone to bites due to factors like blood type, metabolism, body temperature, and individual skin chemistry. These traits, often influenced by genetics, make certain individuals lifelong "mosquito magnets."