Trichophyton rubrum is a fungus that is the most common cause of athlete's foot , jock itch an ringworm. This fungus was first described by Malmsten in 1845. The growth rate of Trichophyton colonies is slow to moderately rapid. The texture is waxy, glabrous to cottony. From the front, the color is white to bright yellowish beige or red violet. Reverse is pale, yellowish, brown, or reddish-brown. Although the tricophyton rubum is the most common of the dermatophytes causing fingernail fungus infections, there are others. Tricophytum mentagrophytes is the second most common source of fungal nail infections from the dermatophyte group.