The hair of many newborns falls out during the first few months of life. This baby hair is replaced by permanent hair. Babies from 3 to 6 months of age commonly rub off a patch of hair on the back of their head due to friction during head-turning against the mattresses of cribs, playpens, and infant seats. The hair grows back once they start sitting up. Hair can be lost because of vigorous hairbrushing, hot combs, tight pony tails, or braids.
Hair follicles are very sensitive to stress.
The hair falls out from all parts of the head over the next 3 or 4 months. After the hair stops shedding, it takes another 6 to 8 months for all of the hair to grow back. The whole cycle takes about 12 months. This type of hair loss is called telogen effluvium.