Hair loss related to internal diseases is generally temporary and often fully reversible. An iron- or protein-deficiency induced hair loss may be cured by simple substitution. In acute internal diseases, fever and after operations the patients may expect complete recovery of the hair loss without therapy. Symptomatic alopecia due to chronic diseases has a different prognosis and is dependent on the severity and character of the underlaying disease. If the systemic disease can be cured the hair loss may be decreased. Treatment and diagnosis of the systemic disease is recommended to be performed in cooperation with experts of internal medicine, oncologists and specialists of endocrinology.