My mum has very bad cracks on her heels and on her thumbs. What can she take and what can she put on them?
A few things I would try for your mother's skin would be external use of salves with herbs such as comfrey, chickweed and plantain. These herbs are all very healing and beneficial for the skin. Internally, if she is not, it is always a good idea to start drinking daily infusions to help balance the body and create an environment within for healing to take place. I am including a link for infusions if you are not familiar with them.
Also burdock root is an wonderful ally for skin conditions - You can include burdock root infusions or use burdock root or burdock seed tincture - (20-40 drops up to 4 times a day). I would also incorporate dandelion greens and the burdock root as food. The dandelion is wonderful sauteed up as one does with other greens and I always throw some burdock root into stocks, soups as well as slice up and roast.
Just let us know if you need any further assistance.
Wise Woman Team