Are there any precautions before and after the procedure for melasma and blemishes?

Now that I’ve turned a new decade, there are spots that even makeup can’t cover up. I’ve finally decided to bite the bullet and get treatment for my melasma and blemishes, so I’m currently looking for a clinic. However, now that I’m actually trying to make an appointment, I’m a bit scared that my skin might get thinner or darker. For those of you who have had melasma and blemishes removed, are there any precautions I should be aware of before I go? For example, things like not being able to wash my face for a few days or absolutely avoiding sunlight. Since I’m in my mid-40s, I’m worried that recovery might be slow, so I would be very grateful if you could share any tips for aftercare or precautions for getting rid of melasma and blemishes cleanly in the comments beforehand. ^^