Hair is a modified form of skin. While a child's hair can be a variety of colors such as blonde, red or brown, and can be curly or straight, the mechanisms for her hair growth are largely the same. By the time she grows up, hair grows everywhere except on the lips, hands, eyelids and foot soles.
Color
A child's hair color often matches his skin color. Many boys with darker skin have black or brown hair, while many blonds have lighter skin. His hair color is usually determined by the color of one or both parents' hair, according to KidsHealth.org. Color reflects the distribution as well as the amount of melanin in the child's hair cortex, so kids with blond hair have only a small amount. This is the same melanin found in the skin.
Process
A child's hair grows as new cells are formed at the base of her hair's root. The cells multiply and form a tissue rod in the skin. That rod moves upward through the skin as new cells form underneath, according to KidsHealth.org. As the rods move, they get cut off from the nourishment supply. They then form a hard protein, called keratin, and the hair cells die. Keratin and the dead cells form the child's hair shaft.
Growth
A child's hair grows about a quarter-inch each month on average. Each hair can grow for up to six years before falling out. A new hair grows in its place, in most instances. A child's hair length depends on the length of her follicle's growing phase, which can be two to six years. There's a rest phase of about three months following the growth phase. Usually about 85 percent of the hairs on the head are in the growth phase at one time.
Features
The size of a child's hair follicles determines how thick or fine his hair is. Large follicles mean thick hair and narrow mean fine hair, according to KidsHealth.org. Hair shape determines whether your child has straight, curly or wavy hair, according to Keratin.com. The cross section for straight hair is circular; the cross section for wavy and curly hair is a flat oval. Curly or wavy hair are aligned, meaning curls all go the same way, because hair follicles in the child's skin are aligned in the same direction, according to Keratin.com.
Puberty
Puberty can cause changes in head and body hair. Most hair follicles are attached to sebaceous gland, or oil glands. The glands' oil can makes hair shiny as well as a bit waterproof, according to KidsHealth.org. However, during puberty the glands can overproduce oil and make the child's hair look greasy.
Growing hair in new places on the body can be one of the first signs of puberty, according to PBSKids.org. For boys, facial hair often begins with a thin, soft mustache. Pubic hair also grows in gradually and thickens and curls as the adolescent matures, and arm and leg hair thickens and likely darkens. Hair growth on the chest, bottom and back usually comes toward the end of puberty. However, each boy will grow hair on a different schedule, so back hair that comes before a mustache is not a concern, advises PBS.org.
Girls typically grow underarm hair and pubic hair that starts out soft and light during puberty. The hair on arms and legs tends to darken and thicken, too. Body hair on both boys and girls may not match head hair color, which is normal.
Hair Loss
Children can experience hair loss. This can have many causes, including harsh chemicals used to perm or color hair, braids and ponytails that are too tight, combing or brushing the hair too hard, pulling and twisting on the hair by the child, or a medical cause. Stress, surgery or fever can cause telogen effluvium, in which more hairs fall out than grow back. Hair growth usually normalizes within six months, according to KidsHealth.org. Cancer treatment, ringworm, which is a fungus on the scalp, hormone problems and alopecia areata, in which round patches of hair fall out, are other causes. Alopecia areata is believed to be an immune system response, and in most cases hair grows back.
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