Can you take penicillin for an athletes foot?

Penicillin has no effect on the fungus that causes athletes foot. Penicillin itself is derived from a fungus. Penicillin is anti-bacterial, it affects bacteria. Penicillin may be used if the athletes foot is serious enough to cause a bacterial infection. Anti-bacterials can cause athletes foot and other fungal infections to worsen by killing the "good" bacteria we all have on our skin and in our bodies. Some of those bacteria feed on fungi.