Why do hair grow only on the head but not elsewhere?

This is a "classic" child question or an adult question. So do you know why?

Hair grows millions of strands on the head but there is no one on the palm, the foot.The reason is that these skin areas have a special molecule that prevents hair and hair growth.

The hairless areas of our skin secrete a special type of molecule called "inhibitor" . It's a protein called Dickkopf 2 (DKK2) .

In areas of the hands, the feet have a special molecule that prevents hair and hair growth.

Usually WNT signaling pathways are responsible for activating hair growth in our bodies, but "skin in natural hairless areas causes inhibitors to prevent WNT from doing its job" , Church Professor of dermatology Sarah E. Millar, of the University of Pennsylvania School of Medicine and Pharmacy (USA), author of the study said.

According to Professor Millar, the WNT signal is very important for the development of hair follicles, preventing hairlessness and turning it into hair.

Millar's team analyzed rat skin and found the DKK2 protein to be very high in hairless areas. Similar to mice, humans do not grow hair in the wrist / leg area, while other mammals, such as rabbits and polar bears, have feathers.

When comparing the DKK2 expression in the rash of rats with rabbits, the scientists found that WNT still exists but less than the haired area.

The team hopes this finding could help other scientists have more ways to study hair growth further. This can be effective in treating or stimulating hair growth in areas of burned skin.

"This study is the latest result to answer the question of why hair just grows and grows a lot on the head but nowhere else. In the future we will add new evidence to explain this , " Follow Millar.

The results of this study are published in Cell Reports.

Earlier, in May, researchers at the National Institutes of Health and the University of Alabama, Birmingham (UK), came up with a new reason for our hair to fade. It is due to each person's immune system.

Melanin is responsible for determining the color of hair made up of melanocytes. When our hair falls out, stem cells add melanocyte cells to new follicles. But when stem cells stop working, hair pigments are no longer maintained as they were at first, causing it to gradually fade.