A mild sunburn sensation after your treatment is considered normal
Blistering due to the pigmented area receiving too much light and heating up too much which can lead to:
Hypopigmentation (lightening or loss of color) which is usually permanent, as well as hyperpigmentation (darkening of the skin) which can usually be treated
Possible darkening of blemishes which is usually temporary
Hairloss in the area treated (which may actually be what you’re after)
Bruising in the area treated