You might need some oiling from the inside...? Mercury is really bad for depleting essential fatty acids which can cause the dry skin problems (lips included). So that is another thing you might want to look at. Candida can do it as well, so be careful of sugars in your diet (even natural ones).

I make sure I have enough fats in my diet (the right kind) like fish oil (mercury free brand), flaxseed oil (I just add a teaspoon to my yoghurt and stir it in), butter, olive oil and things like that.

Mercury can really cause dry skin, so sometimes you have to counteract it's action by oiling yourself up internally. Other than that, not sure of the answer.