Thanks Mohammad u have actually asked the first technical question here... for people who doubt me being a doc this answer shud clam them up....

Cortisone is steroid and its used to reduce inflammatory process anywhere in the body... however the flip side is it shud be used with caution under a physicians guidance... cos apart from several side effects it can ( on prolonged usage) compromise immunity, cause increase in body weight due to water retention and make you prone to other super added infections...

yes a combination therapy is better but better than a topical antibiotic try a topical anti fungal like nystatin...

foot fungus is rampant in hot humid conditions like middle east... prevention wud include usage of open airy sandals for people who sweat a lot in their feet and daily use of fresh dry socks for people who use closed tight shoes....

hope this helps....

As long as you are trying hard, you are never failing....
The only failure is failing to try harder.....