I wonder how does the crew take a haircut? Is there a beauty parlour in the Voyager? Like Kes, she has a stylish hairdo.
We don't know.
One popular theory is that they used the holodeck and a holographic barber, with safety measures turned off so that the hologram's scissors could really cut their hair ... but the popularity of this idea is probably more due to its 'coolness' than to any actual canon evidence supporting it.
This forum poster claims that Janeway cut her own hair in the Star Trek novel Captain's Table: Fire Ship. But a perusal of the book itself suggests that the next poster is correct and she actually lost her bun in a fire rather than cutting it off herself.
"Computer, BEEP One pair of scissors WRRRRRRRR replicates scissors Jokes aside, Starfleet has quartermasters and presumably the members aboard are trained to handle thier own personal grooming. Since Voyager left without a FULL crew complement during it's mission in the badlands, they left without a host of various people, including counselor, etc, or a barber. But hair care shouldn't be a difficult task, women mostly wear their hair tied back.