Hello Thanks for writing to HCM Since Melacare cream has hydroquinone, it undergoes strong reactions when exposed to the sun. If one is exposed to the sun while having the cream on, it will thus result in photo-allergic reactions,this will result in darkening of the skin. Thus, it’s advised to apply sunscreen cream if you plan on going outdoors. Failure to do this will result in considerable harm to your skin because it will darken. In the event that you get skin irritation from using the cream, then it’s recommended to stop using it for at least a month Hope i have answered your question Take care