Oily hair is the result of an oily scalp. Some conditions that may cause an oily scalp include hormonal imbalances, certain diseases and genetic predisposition.
Sebaceous glands located in the skin tissue of the scalp are responsible for producing sebum. When produced in normal amounts, sebum is healthy and moisturizing for the hair. When too much of this chemical is produced, it is absorbed by the hair and causes it to become oily. Conditions, such as puberty and pregnancy, may result in hormonal imbalances, which cause the scalp and hair to become oily. When imbalances are corrected, sebum production returns to normal levels.
Certain diseases or disorders that affect the pituitary glands, adrenal glands or ovaries can also cause oily hair. Oily hair may also be a result of genetics. If the hair is not shampooed on a regular basis, dirt and oil builds up on the scalp, causing oily hair. Brushing the hair too often does not cause an oily scalp, but it does distribute oil throughout the hair.
Oily hair may cause acne or dandruff. Hair that is too oily may appear stringy or fall flat. It is also difficult to style. Oily hair that is untreated may ultimately lead to hair loss.