Shining, lustrous hair and strong, even nails are attractive and desirable natural adornments. The condition of your hair and nails can also be indications of health or illness, and their growth can be affected by environmental or genetic factors.
What They're Made Of
Hair is made up of a protein called keratin. Each hair consists of three layers. The inside layer is the medulla, which is usually lacking in very fine or blond hair. The cortex contains a melanin pigment that gives hair its color. The outer layer -- the cuticle -- is made up of overlapping transparent cells that protect the cortex. Nails are also made up of keratin. The nail matrix is under the skin behind the nail. The visible part of the nail is called the plate. The crescent moon at the base is the lunula. The cuticle is the thin tissue over the base of the nail plate.
How Hair Grows
Human beings have approximately 5 million hair follicles, but only 100,000 are on their heads. The rest are everywhere on the body except on the palms of the hands, the soles of the feet and the lips. Human scalp hair grows at a rate of 1/2 inch each month, or 6 inches a year. Hair growth starts at the bulb, and cells in the bulb turn into hair fiber cells. The bulb is the only part of the hair that is alive; once it grows out of the bulb, hair is dead. Hair grows in three cycles, with each follicle producing one hair that grows for two to six years. Then the bulb goes dormant for three months and the original hair falls out. People normally shed about 100 hairs every day. A new hair is formed during the growth phase.
How Nails Grow
Fingernails grow faster than toenails, and they grow faster on the dominant hand. Healthy fingernails grow 3/8 inch each month, while toenails are slower, at 1/16 inch. Age, gender, heredity, activity and even the time of year affect the rate of nail growth. Men’s nails grow faster than women’s, and nails grow faster in summer than winter. Disease, nutrition, medications and trauma -- including wearing false nails for too long -- can affect the growth of nails.
Common conditions that adversely affect the hair are unusual shedding; baldness and its opposite, hirsuitism, or excessive hairiness; and developmental problems. Excessive shedding can be the result of pregnancy, illness, chemotherapy and some medications. Baldness may be the result of genes and can be treated with prescription medications and hair transplants. Ringworm is a fungal infection of the scalp. Overprocessing by coloring, perms and heat treatments can also damage hair.
Nail Diseases and Conditions
Nails, especially toenails, are subject to fungus infections. Ingrown nails can result from careless trimming, nail biting or even ill-fitting shoes. Keep nails clean and cut them straight across to avoid ingrown nails. Changes in the nails, such as thickening or discoloration, can indicate health problems such as heart conditions, lung problems, liver or kidney disease, anemia or diabetes. Any change in nail color, shape or thickness; bleeding; or discharge requires medical attention.
- Texas Collaborative for Teaching Excellence: A Close Look at the Properties of Hair and Scalp: Topic 3: Chemical Composition of Hair
- Better Health Channel: Nails -- Fingernail and Toenail Problems
- Better Health Channel: Hair
- Hairfinder: How Fast Does Hair Grow?
- American Academy of Dermatology: Nails