The transplanted hairs in a FUE hair transplant do not fall out anymore because they are taken from areas of the head that are resistant to the hormone dihydrotestosterone (DHT). DHT is one of the main causes of androgenetic hair loss, which is most common in men and women. In this type of hair loss, the hair follicles shrink over time under the influence of DHT and eventually produce no more hair. The hair follicles at the back of the head and the sides, however, are usually genetically resistant to DHT and are not prone to this type of hair loss. Therefore, they can be successfully transplanted into the areas affected by hair loss, where they continue to produce hair. It is important to note that while the transplanted hairs are permanent, hair transplantation does not stop the progression of hair loss in the untreated areas of the head. Therefore, it may be necessary for some patients to undergo multiple hair transplants or continue medical treatments for hair loss to maintain the overall result.