Totally agree with what everyone's saying about acids. I think the thing is, if you've never used them before and you start with them, they can make a very big difference to your skin immediately, almost like they're taking off a layer to reveal lovely smooth skin underneath. So you feel like you should use them every day to keep that up. But after a while, it feels like they're stripping away too much and you can start to get some redness. That's my experience anyway. I still like to have them in my routine once or twice a week but every day is too much. Paula's Choice Salicylic Acid for me. My routine is now a mix of some of the more expensive serums, oils etc. but a lot of it I've gone back to basics and back to the stuff I've used for years that I know does the job at a good price. It's eye watering how much some people must be spending on the high end stuff for every single step of their routine.