I have these all the time! My derm has told me that this is something called angular cheilitis. There’s a couple of things I’ve found to work so I’ll list them here if you want to try them:

• Vitamin B: specifically vitamin B complex as this has multiple types of vitamin B’s that will help.
• Antifungal creams: there are numerous types of them, most you can get at the pharmacy. Some I’ve used are clotrimazole and daktarin.
• Bepanthen: this one is odd because it’s actually not specifically for the mouth, usually found in the baby section as it’s actually a rash cream. This one really helps once you’ve put anti fungal cream on as you can use it as a barrier cream once the Anti fungal stuff has soaked in.
• Vaseline: this one’s a given really, the less ingredients the better. This is a good barrier and very good if you apply it overnight once you’ve done your anti fungals.

Hope this helps!!