Bottom if foot itches all the time only right one?

Fungus, neuropathy . Or other types of dermatitis. Is there any sign of inflammation or scaling of skin? If this persists, see physician for diagnosis and treatment.
Itching. I suggest you have your family doctor do a fungal culture on it first. If it is negative try an over the counter cortisone cream for a week. If it resolves then you are dealing with some form of a dermatitis.If the culture is positive .Your doctor will prescribe an anti fungal medication to resolve it. If neither of these approaches resolves it.Then a biopsy is recommended.