Lemon Juice on skin and hair

I don't know about the skin accept to say that ingesting a lot of citric acid can cause your skin to produce more oil, I don't know about topically. For your hair, yes it will lighten your hair. Depending on how dark your hair is it could get stuck in an orange phase. Also it works better in the sunlight, if you are able to lay out in the sun, if not use a blowdryer.

Yes lemon juice will lighten your hair if you squeezed the juice in your hair and dried it. The skin treatment I am not sure about.

I have never tried the hair treatement myself, but when I was younger a friend of mine used it. She had dark brown hair (almost black) and after she used it a few times there was a slight color change - made her hair look orange. As far as the lemon jucie for skin lightening, I think I would go with a true product that you get from your doctor. Since lemon juice is so acidic there is a good chance that it was cause irritation and you won't get the results that you are looking for unless you sue it over time.