Fluid-filled blisters can also form. Because the fungus may cause the skin to crack, athlete's foot can lead to bacterial infection, especially in the elderly and in people with inadequate blood flow to the feet. It's much more common in men than in women and develops more frequently in warm weather. The infection produces red, ring-like areas, sometimes with small blisters in the skin around the groin and over the upper, inner thighs. The condition can be quite itchy and even painful.
Recurrence is common because the fungi can survive indefinitely on the skin.
Even with proper treatment, a susceptible person may have repeated infections. Scalp ringworm is caused by Trichophyton or Microsporum, another fungus. Scalp ringworm is highly contagious, especially among children. It may produce a red scaly rash that may be somewhat itchy, or it may produce a patch of hair loss without a rash. Nail ringworm is an infection of the nail caused by Trichophyton.