How Does Hair Grow?Does It Grow from Its Root or the Tip? 

Daniel's family went to the park for a picnic this weekend and everyone was exhausted. As soon as he got home, Daniel lay on the sofa and didn't want to move. With mom's repeated nagging, he finally took a bath.

After the shower, Daniel felt better and rejuvenated. He insisted on helping mom dry her hair. With a hair dryer in one hand and mom's long, dark and silky hair in the other, Daniel worked carefully while talking with mom about the funning things in the park. Suddenly, he found something and said, "Mom, you have a white hair." Mother looked at it and asked Daniel to pull it out. The white hair fell down with a little pulling force. It is half-black and half-white. Daniel felt strange and said, "Mom, this hair is not all white."

Mom wasn't surprised, "Our hairs grow slowly from the hair follicles at the roots. The hair follicles secrete a substance called melanin, which makes the hair black. But as people get older, the cells that produce melanin slowly age and die. Without enough melanin, the hair therefore turns white."

Daniel didn't understand all of a sudden and asked, "You mean our hair grows from its root like we pull radishes, instead of growing from the tip like twigs?"

Mom nodded and said, "Yes, hair grows from the scalp. The blood carries nutrients to the hair follicle cells in the scalp, which divide and grow into hair."

Daniel asked curiously, "How many hairs do we have? If I pull a hair out, will I lose one forever, and will new hair never grow?"

Mom waved her hand and said, "Don't worry. We have about 5 million hair follicles, of which 100,000 are generally on the scalp. The number is basically determined at birth. New hair follicle cells will replace the dead cells to grow hair. But when we get to a certain age, the follicle stops growing new hairs. So the hairs of the elderly are generally white and sparse."

Daniel touched his hair and asked, "How long does it take to grow new hair?"

Mom took over the hair dryer and began to dry her hair, "It depends on the metabolic rate, gender, age, and nutritional status of different people. Normally, hair grows 1 centimeter per month. Don't worry about it. We lose 50 to 100 hairs per day. It doesn't matter we lose hairs as new hairs will grow."

"But sickness or drug stimulation may slow the growth of hair. And some diseases may make the hair malnourished, turning it yellow and dry."

Daniel was a little confused, "Our hair is black and we can't wash it white. So why should we wash hair?"

Mom laughed and explained, "Haven't you noticed what your hair looks like when you haven't washed it for a long time? It's greasy as if there is a plastic film on your scalp. Hair secretes sebum as it grows, and when the sebum accumulates to a certain extent, we have to wash it off. And dandruff, we have to wash it off too."

Author: Huang Jing