A chemical exfoliant peels away at the top layers of your skin. In terms of safety, you can use the gentlest of exfoliants, like salicylic acid, once or twice a week.
In fact, many dermatologists will recommend a chemical exfoliant over a physical exfoliant for sensitive skin just because of the harsh scrubbing that some do with physical exfoliants. For the more than 60% of women who have sensitive skin, it can make a huge difference to our skin to not be scrubbing away at it with rough materials.