Can salicylic acid be used safely direct on skin?
You can use it directly on skin if it is in a medium formulated with under 5% Salicylic acid, although I would recommend 2%. It can be applied to an area and rinsed off at up to 6% and it is used in some face peels at higher doses, but this is quite likely to cause irritation. High percentages can burn the skin and make it more vulnerable to UV radiation.
It is a beta hydroxy acid, so it is good at loosening the top layer of dead skin and smoothing the complexion/fading pigmentation. It is also an effective acne treatment. 10% to 18% concentration is used to remove warts.