When it comes to pollen, dog hair, and the other everyday culprits of common allergies, there are few who don’t fall victim to sneeze attacks and itchy, red eyes. According to two papers recently published in the American Journal of Human Genetics, it’s because one of our early Homo sapien ancestors mated with a Neanderthal.

While few would brag about hosting Neanderthal genes in their DNA, we might not be alive were this not the case. Janet Kelso of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, led one of the two teams that searched through human DNA from Neanderthals, as well as another early human, the Denisovans, for genes involved in regulating immunity. According to Kelso,

“When modern humans were coming out of Africa, they met the Neanderthals who were living at that time in Europe and western Asia, interbred with them and carried with them some of the Neanderthal DNA as they migrated out into wider parts of the continent.”

Both teams identified three genes from these two extinct groups that play a role today in controlling a part of the human immune system known as innate immunity. “When the body detects that there is some foreign substance in the body, these are the guys that react immediately,” Kelso explains. “It kind of calls in the big guns.”

However, it appears that these same bits of DNA are what cause our immune systems to overreact to things like pollen and animal hair. To read more, head over to NPR.

Featured image via Flickr.