I was asked to put on the Cosmelan mask for 12 hours. After that, my face is swollen, red and itching. Is it normal?

It’s really hard to determine exactly what is happening without a proper exam or at least some photos, but normally Cosmelan is applied to the face for no more than 8 hours for dark skinned individuals and 4-6 hours for light skinned individuals, so having it on for more than 8 hours no matter what skin color you are isn’t the norm and you may be having a reaction to that. I would suggest you see a cosmetic doctor for a thorough evaluation.

if you were not given proper instructions or skin care I suggest you see an expert to determine what you next best steps are.  Dr. Emer.