I used melacare last 3 weeks. In my neck some black patches and irritation appear after using? (Photo)

Pls see these black patches after using melacare. Am using since 3 weeks now. My face is ok but neck got worse. am using sunblock "day long "50+ I went to dr but he gave me epiduo and told me to use 1night melacare and 1night epiduo. Before I was using melacare twice a day without asking dr. Am now very upset for these black patches on my neck. It is irritating and feeling like someone throw salt on wound whenevery I apply melacare,epiduo or even wash with gentle wash it hurts..pls help me

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