Alpha-Arbutin and Kojic Acid long term usage side effects?

I used Hydroquinone for 8 weeks on my face and noticed it made my melasma patches darker when I stopped using it and was exposed to UV light - even with a 22% zinc oxide on daily. I have now stopped using Hydroquinone and am looking at other alternatives such as kojic acid and or alpha-arbutin. Are these products toxic long term? Do they affect skin sensitivity to the sun long term i.e. make the melasma patches darker when exposed to UV light and or if I stop using it? Thanks, Mary