Monique I don't think yoghut is natural alpha hydroxy but contrary is base & contains bacterias not enzymes. Natural alpha hydroxys are fruit based sugars which are acidic usually with some extra vta C & or rosehips thrown in. I would think that adding yoghurt is benefical to the skin in general (I add it to my hair henna treatment) & mixing with lemon juices would help to apply. Lemon juice of itself would be a fruit acid
Unless there's more about yoghurt in this application that happens when mixed; I know when you mix kiwi with youghut it changes the composition radically & I'm not sure I remember the purpose as a friend of mine was using it to change her stomach composition - possibly to up acidity......

So, will this lighten your skin as well as the sunspots? I HATE my sunspots but like to have a little color to hide the lovely cellu-lumps. I use lots of sunscreen but am at the pool a lot. Thinking it probably does both.