Common causes of hair loss include:

• Family history. In most cases, hair loss is inherited. That means it's passed down from one or both of your parents. This is called male-pattern or female-pattern hair loss.
• Stress, including physical stress from surgery, illness, or high fever.
• Chemotherapy. This is powerful medicine that destroys cancer cells.
• Damage to your hair from pulling it back too tightly, wearing tight braids or ponytails, or using curling irons or dyes.
• Age. You grow less hair as you get older. Hair also gets thinner and tends to break more easily as you age.
• Poor diet, especially not getting enough protein or iron.
• Thyroid diseases, such as hypothyroidism and hyperthyroidism.
• Ringworm of the scalp, which is common in children.