Patchy baldness can last from a few months to a few years, so there is no standardized time frame for how long it takes for hair to grow back. Patchy baldness, also commonly known as “ghost shaving”, is a relatively common form of non-scarring alopecia, which is considered to be related to autoimmune, hereditary, emotional stress and endocrine factors. Clinically, it is usually characterized by sudden onset of patchy alopecia with clear boundaries, no scarring of the alopecia area, and no inflammatory reaction. In the case of patchy baldness, the aim of treatment is to stop the progression of the disease as far as possible, slow down the symptoms of hair loss and promote hair regrowth. However, the course of the disease can last from several months to several years, and most patients are able to regrow their hair, but it may come back again. So there is no exact time as to how long it takes for hair to grow back in baldness. It is recommended that after the occurrence of baldness, patients can cooperate with doctors to carry out appropriate treatment according to their own conditions, and should not delay the condition, so as not to aggravate the symptoms.