One of my research interests. There are actually many different types of hair loss patterns. Each with their own individual treatment and management.
We use specialised tests and equipment to diagnose these. Most hair loss is reversible, however some types such as cicatricial alopecia are irreversible. I always tell my medical students, if they are unsure of the type of hair loss a patient has, they should refer them urgently to a dermatologist for prompt diagnosis and treatment. Cicatricial alopecia is indeed a dermatological emergency.