Mosquitoes can smell you better at night. Science may have finally figured out why. Apparently, a chain of odorant-binding proteins (OBPs), which help mosquitoes to smell humans, accumulate in their systems in greater quantities at night.
OBPs are believed to help transport molecules to the mosquito’s olfactory receptors. In addition, the mosquitoes retain their sensitivity to odors which do not require OBPs as well as the levels of proteins that are used to smell those odors.
By using the smell of our bare skin and the carbon dioxide that we emit, mosquitoes can actually smell us from about 100 feet away.