Is it a disease or skin condition?

Sounds like Athlete's foot which is caused by a fungus. Athlete's foot can spread to other parts of the body than the feet. The hydrocortisone will not help because it is not an anti-fungal. He could try an over the counter anti-fungal cream. If it doesn't improve within a week or two, he does need to see a doctor. Recurring fungal infections can also be a symptom of diabetes or other circulatory problems.