Piedra, which means "stone" in Spanish, is an asymptomatic superficial fungal infection of the hair shaft. Piedra is classified into 2 types, black piedra and white piedra. The source of infection in black piedra appears to be Piedra Hortae, found in the soil and has also has been traced to organisms in stagnant water and crops. The source of infection for white piedra is Trichosporon and that remedy should be used.

Black piedra is most common in tropical regions such as South America, Far East, and the Pacific Islands. White piedra is more common in temperate and semitropical climates, such as those in Asia, Europe, Japan, and parts of the southern United States.

Both types of piedra ultimately may lead to hair and scalp infection causing the hair to break because the shaft is weakened by cuticular penetration.

This remedy addresses the Piedraia hortae, please see the Trichosporon section for the cause of white piedra.