Excessive hair loss can occur due to a number of reasons. It is a temporary type of hair loss, which can be related to a prolonged illness or surgery, medication, stress etc. Following are a number of factors that can cause excessive hair loss in men and women:

1. When male and female hormones known as androgens and estrogens become out of balance it results in excessive loss of hair. This problem can be overcome by treating the imbalanced hormones.

2. Thyroid diseases can give rise to excessive hair loss due to over activeness or under activeness of thyroid glands

3. Excessive hair loss often occurs for few months after the delivery. This hair loss is also related to hormones because during pregnancy high level of hormones stop the normally shedding of hair which falls out when the hormones return back to the pre-pregnancy levels.
4. Hair loss is a common side effect of many medicines. Although the growth cycle comes back to normal when the medicine is stopped but during the treatment it can cause excessive hair loss. Some of the common medicines that cause excessive hair loss include blood thinners, medicines for gout, chemotherapy, excessive vitamin A, birth control pills and antidepressants.
5. Different types of fungal infections of the scalp also result in excessive hair loss especially in children.
6. Excessive hair loss is an early symptom of many diseases like lupus or diabetes