Prostaglandin D2 is primarily used in medical research to study its role in various physiological and pathological processes. It is known to play a significant role in regulating sleep, as it promotes the induction of sleep in animal models. Additionally, it is involved in the inflammatory response and is studied for its effects on conditions such as asthma and allergic reactions. In dermatology, it is explored for its potential in treating hair loss, as it has been found to inhibit hair growth. Furthermore, it is used in the development of drugs targeting the DP1 and DP2 receptors, which are implicated in a range of diseases including cardiovascular disorders and cancer.