What can cause a secondary infection on athlete's foot secondary?

Bacterial: Bacteria can cause a secondary infection. The fungus sets up an optimal environment for a bacterial infection to occur.

Bacteria: If you have athlete't foot or tinea, in between your toes, this area is very moist and eventually the skin will break down and opens up. Since our feet have the most bacteria in our body, they enter through these breaks in the skin and lead to 2ndary foot infections. Any cracks on the feet may also allow this to happen. At this time you need antibiotics and antifungal medication to treat both.

The cracks in skin: Caused by athlete's foot can allow bacteria to enter and cause cellulitis, an infection of the cutaneous tissue.

Foot infection: Athlete's foot is a fungal infection that can break down the normal covering of skin and render the area more susceptible to a secondary infection. Secondary infections can include bacterial infections.