Do you tend to sneeze when flowers around you bloom during the spring or a cat comes nearby? Well, researchers at the Max Planck Institute for evolutionary Anthropology in Leipzig may have found the cause behind this allergy of yours.

The researchers say this condition could be due to a DNA factor, resulting out of encounters more than 40,000 years ago between humans and their burly cousins, the Neanderthals, or their close relatives, the Denisovans. The gene may have left the present day humans more susceptible to sneezes, itches and other forms of allergies.

Through recent studies, many groups of scientists had been trying to figure out what impact that Neanderthal DNA factor could have on modern humans.

According to researchers, the genes may have spread through modern humans when small groups of pioneers who left Africa met Neanderthals, who were already long at home in Eurasia. This genetic legacy led to all non-Africans today carrying 1-6% of Neanderthal DNA.

The Neanderthals, unlike the new entrants, had spent 200,000 years adapting to life in the region and their immune systems had become in sync with the new infections they faced. Three strands of genes are said to be quite similar in modern humans as well as Neanderthal and Denisovan. These genes may have strengthened the body’s first line of defence against pathogens such as bacteria and fungi, but with this kind of DNA seem to be prone to the aforesaid type of allergies as their immune system is overly sensitive.

Janet Kelso, who led the research, said, “A small group of modern humans leaving Africa would not carry much genetic variation. You can adapt through mutations, but if you interbreed with the local population who are already there, you can get some of these adaptations for free”.