Shea butter is the fat pressed from the nut of the West African shea tree, solid at room temperature and melting on contact with skin. Where an oil sinks in and disperses, shea butter forms an occlusive layer — it stays on the surface and stops water escaping.
That is exactly what damaged foot skin needs. A crack in a heel will not close while the skin around it keeps drying out and pulling apart. Shea butter holds the moisture in long enough for repair to happen.
The book pairs it with ingrown toenails, and the logic is sound: soft, supple skin around the nail fold is less likely to be pierced by a nail edge, and less likely to become inflamed when it is.
