Sweet Blood?

“Sweet blood” is one of those household myths that have grown up to explain something that most people find unexplainable, like why toast always seems to land butter-side down. People look for a simple answer that can explain the many myriad of forces at work that they can’t see. Unfortunately, those simple answers are usually hokum and don’t stand up to scrutiny.

In the case of sweet blood, how would a mosquito know a person’s blood was “Sweet” before it bit them? If sweet blood were a reality, everyone in the room would get bitten once, and then one person from then on.

The truth is that there are many forces at work that only the mosquito knows about for sure, but here are some things that we do know mosquitoes are attracted to:

• Colors that contrast strongly with the background
• Sweat
• Carbon dioxide
• The scent of lactic acid
• Heat
• Motion

So maybe you were wearing a more contrasting color, were moving more, were breathing a little heavier (and therefore stirring up more carbon dioxide and lactic acid scents than anyone else) and were registering as a little warmer than anyone else. Who knows? Only the mosquitoes.

There is also some evidence that those with Rh-negative blood tend to get bitten less than anyone else, but this is probably a circumstantial effect.