The most common cause of hair loss is hereditary conditions, such as male-pattern baldness (androgenetic alopecia) in men and female-pattern hair loss in women. These conditions are inherited and result in a gradual reduction of hair follicles, leading to thinning and eventual hair loss.

Certain medications and medical treatments may cause hair loss as a side effect. This can include chemotherapy for cancer treatment, as well as medications for conditions such as arthritis, depression, heart problems, gout, and high blood pressure.

Physical and emotional stress can contribute to hair loss. Significant stressors, such as a traumatic event, illness, or major surgery, can lead to a temporary condition known as telogen effluvium, where a large number of hair follicles enter the resting phase simultaneously, resulting in increased shedding.

Hormonal changes and medical conditions can contribute to hair loss. For example, hormonal changes during pregnancy, childbirth, and menopause can affect hair growth. Medical conditions such as thyroid disorders, alopecia areata and polycystic ovary syndrome (PCOS) can also lead to hair loss.