How to use lactic acid?

[Byfleet]

I have just got The Ordinary lactic acid 10%. I assumed I would put it on my skin after washing my face last thing at night, and then leave on over night in the same way I use granactive retinoid. However the instructions say to avoid prolonged contact with the skin. Does this mean you have to wash it off again ?

Bump

www.beautybay.com/edited/the-ordinary-lactic-acid/#:~:text=Apply%20a%20thin%20layer%2C%20once,gradually%20building%20up%20to%20daily.

This says after toner before moisturiser so implies its left on.

Thank you!