Don't worry, dear, any either water or juice fasts will improve the condition of ur skin. Ur dry skin possibly is an indicator that something should be fixed in ur body. DURING a fast the condition of ur skin can be changed to a better side or another way round. Don't worry about that too much coz it is just FAST and everything can happen during it. Also bare in ur mind that as soon as ur fast is over and the condition of ur skin still doesnt meet ur expectations then think about doing something else like EATING VERY HEALTHY FOOD mostly raw and, as I mention everywhere (I guess:D), IN RIGHT COMBINATIONS. Ur skin will be just glowing! PROVED based on my previous experience! :)))
Also try to wash ur face only with spring or mineral water and, while having a shower, try not to put any tab water on it. I also had very dry skin but as soon as I started using spring water my skin is not dry anymore - what a difference!
I don't remember whether I mentioned this web site to u or may be u heard about it.. Go to http://www.cosmeticdatabase.com
and have 'fun'. Something to think about!