I'm not sure if they study it, but there is cosmetology. It's the study and also the application of beauty treatment.
I studied cometology in school. It is beauty treatment.
Hello, do you really have purple hair? No, do you practice changing hair colors, which is the practice of hair dyeing? Neither, I don't even know who to go for it! So a hairdresser can do it but it can also be done at home. Oh interesting, don't those people study something related to beauty treatment?
Cosmetology (from Greek , ''kosmētikos'', ''beautifying''; and , ''-logia'') is the study and application of beauty treatment.