I started using Cosmelan last week and I have an appointment for Botox tomorrow. Can I do it without any problem or reaction?

There should be no problem getting Botox injections while on Cosmelan. You should not have any reaction .

Yes, you can have Botox after Cosmelan. If you just did Cosmelan, you should have a chemical peel or lasers at this time for long-term improvement. I recommend getting a formal evaluation with a cosmetic dermatologist. Best, Dr. Emer

It should be perfectly fine to receive Botox after starting Cosmelan treatment.  Only caution would be if your skin is very dry or fragile, otherwise, no problems at all.  Cosmelan is a great way to get rid of excess pigmentation in the skin.