Intestinal worms, so-called Helminths (Toxocara Canis) from animals, actually have an influence on allergy and asthma risk in humans.
The results of the research team at the University of Bergen (UiB) in Norway showed that young people who test positive for this parasite, have a four times higher risk of developing asthma and allergies than others.
"Usually, we consider a 50 percent higher risk as being high, but here we see a 400 percent higher risk," says Professor Cecilie Svanes at Centre for International Health, UiB.
"We do not know why the parasite only influences the young generation in a negative way and not their parents. If we can discover the reason for this, I think we will have solved the puzzle of why allergies have increased enormously over the past few decades," says Svanes.
Many studies show that the numbers of people with asthma and allergies have increased enormously over the past few decades. The reason for this is unknown.
"One of the most common hypotheses is that we have become more in contact with chemicals and less in contact with microbes and bacteria," Svanes explains.
"There are, however, many things that have changed during the last decades. Nobody knows why allergy and asthma levels have increased. The phenomena is happening all over the world. It probably relates to urbanisation among other things."