Why underarms respond faster than the face
Laser is absorbed by pigment in the hair, so the coarser and darker the hair, the more energy reaches the follicle. Underarm hair is among the coarsest on the body, which is why the area commonly finishes in six to eight sessions where the face needs eight to twelve.
Most people see a visible drop in density from around the second or third session, and it compounds from there. The hair that returns between sessions comes back finer and slower each time.
Will it fix dark underarms?
Partly, and it depends entirely on what is causing the darkness — which is the honest answer rather than the one that sells a package.
Where the darkness is really the shadow of hair sitting below the surface, or the aftermath of years of shaving nicks and waxing irritation, removing the hair and stopping the trauma does visibly help. That is a common cause and laser addresses it directly.
Where the darkness is true pigmentation — post-inflammatory hyperpigmentation, friction from tight clothing, deodorant reactions, acanthosis nigricans linked to insulin resistance — laser removes the hair and the pigment stays. That needs treating as pigmentation in its own right, and acanthosis nigricans in particular is worth a medical look because it points at something systemic.
You will be told which of those you have at assessment, not sold a course on the assumption it is the first one.
Practical things worth knowing
Do not apply deodorant or antiperspirant on the day of your session, and leave it off for 24 hours afterwards — the alcohol and the fragrance sting on freshly treated skin and can provoke a reaction that looks like a laser complication but is not.
Shave the night before or that morning. Do not wax or pluck for at least four weeks before your first session, because the laser needs the follicle to still be there.
Skip the gym, hot showers, saunas and swimming for 48 hours after each session. Heat and sweat on freshly treated follicles is the most common cause of the small spotty folliculitis that occasionally follows a session.
Wondering why the hair is there in the first place? Our page on unwanted hair covers the full picture across every area and every method — this page is about what treating it involves and what it costs in Chromepet.