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.
Medical conditions that can cause hair loss include thyroid disease, alopecia areata (an autoimmune disease that attacks hair follicles), and scalp infections like ringworm. Diseases that cause scarring like lichen planus and some types of lupus can result in permanent hair loss because of the scarring. Hair loss can also be caused by medications used to treat cancer, high blood pressure, arthritis, depression, and heart problems.