It's best you seek and advice to a Podiatrist because they are the expert of foot.
Hi there!
There can be dark spots on the feet due to several reasons. Improperly fitting shoes, overexposure to the sun and poor circulation all can lead to dark spots on the toes and feet. You may use pumice stone while bathing. It will help in removing the dead cells and massage shea butter into the dark spots each morning. The shea butter will hydrate the skin promote healthy circulation and diminish the dark spots. If the symptoms are severe seeking the opinion of a dermatologist/cosmetologist will be really helpful.
Take care and regards!