Hair loss occurs when hair is shed at a faster-than-normal rate. The normal hair growth cycle involves an active growing phase followed by a resting phase. Normally about 50 to 100 hairs are lost on average each day, but certain medications or other stressors can cause the hair roots to prematurely enter the resting phase. This can lead to noticeable thinning or bald patches on the scalp or other areas of the body.

While there are many different types of hair loss, the two main types that can be experienced as a side effect of certain medications include:

• Telogen effluvium – The most common form of temporary hair loss that can occur within two to four months of taking a drug or after an illness or stressful event. Hair roots are pushed to the resting state too soon, resulting in handfuls of hair that may fall out, with an average of 100 to 150 hairs shed daily.
• Anagen effluvium – Severe and sudden hair loss that occurs within days or weeks of taking certain drugs (usually chemotherapy drugs). Hair loss is more extensive and can include eyebrows, eyelashes, and other areas of the body. Re-grown hair may not be as thick