By completing the quest Beauty Is Only Scalp Deep, adventurers can access Jandelaine, the Aesthetician, in order to change your hairstyle and certain other cosmetic characteristics at any time. To access the Aesthetician, use a Crystal Bell (in an Inn or other accessible free company or personal housing) after completing the above referenced quest and select the option to summon the Aesthetician. Additional hairstyles beyond those that are part of the character creation can be obtained from various sources including for MGP, from Bronze-trimmed Sacks and Silver-haloed Sacks, for Wolf Marks, and from the Mog Station.
