Here's the academy's list of possible causes of hair loss:

• Stress caused by an illness or major surgery. This type of hair loss often is temporary.
• Changes in hormone levels, such as those caused by pregnancy or a thyroid disorder.
• Use of certain medications, such as blood thinners, antidepressants, oral contraceptives, heart medications, gout treatments or vitamin A.
• A fungal infection of the scalp.
• An underlying disease, such as diabetes or lupus.

-- Diana Kohnle