Oh, one other thing for many is that it can be darker just with heat. There are women that complain when they have to cook with the oven or even they've been outside but in the shade when it's very hot and they get darker 
I'm glad it's getting a bit lighter already !They've all made good suggestions but I've got to agree, using a bit darker foundation will help blend the melasma better than a lighter one. I never had much luck with any of the colored corrective concealers (lavender etc). Most of the just made my melasma patches look gray. I choose one slightly darker than the normal skin and a little lighter than the melasma and it works to blend the edges a bit. But for most days, I just go with foundie .The sun near the equator is much stronger. Hawaii happened to be where I first noticed I had melasma as well. We were stationed there for 10 years. I'm sorry to hear it happened to you. I started out with just a hitler type mustache. I got too much sun after waxing
Then, the spot on the forehead and the derm treated it with IPL. Now I've only got a couple fingers width of my forehead still melasma free. I've got a splotch near the corner of my eye and a couple on my upper cheeks. I've also got a bit of darkening on my chin. I personally think melasma has a mind of it's own but also that you get the best results by sunscreen, vitamin c products and some products that have niacin in them also work (b3) to help lighten things up a bit. Above all, being gentle as any trauma can cause a new spot. Good luck
