The human body contains many natural polymers, such as proteins and nucleic acids. Cellulose, another natural polymer, is the main structural component of plants. Most natural polymers are condensation polymers, and in their formation from monomers water is a by-product.
Alopecia areata is one type of hair loss that typically causes patches of baldness. In some cases, total baldness develops. In many cases, the hair re-grows, typically after several months. In some cases, the hair loss is permanent.
Drugs, including chemotherapy drugs used in cancer treatment, blood thinners, beta-adrenergic blockers used to control blood pressure, and birth control pills, can cause temporary hair loss. Burns, injuries, and X-rays can cause temporary hair loss. In such cases, normal hair growth usually returns once the injury heals unless a scar is produced.