Is Upper Lip Hyperpigmentation Caused by Shaving Followed by Sun Permanent? (photo)

Over a year ago, I shaved my upper lip a bit too thoroughly during my morning shower, went down to the pool and laid out/ went swimming. I was outside only an hour. I had sunscreen on. It stung a bit where I'd shaved.When I went in, I had a tan mustache. Saw a Dermatologist who said I had melasma(same as post inflammatory hyperpigmentation?) I cleared it with apple cider vinegar and athlete's foot cream.I stopped shaving. Went outside for thirty minutes two months ago and it happened again....

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