Piedra is a Spanish word meaning stone. The condition is characterized by black and white nodules located near the base of the hair follicles. In serious cases, the hair breaks into small bits. It was first described by Biegel in 1865, and has been classified into two types:
- Black piedra: This type thrives best in tropical conditions. It is caused by a fungus called piedraia hortae. Its unique symptoms include:
- Dark, stony nodules at the base of the hair
- In severe cases, a metallic sound is produced by the nodules during normal combing of the hair.
- White piedra: It is caused by a species of fungus known as Trichosporon beigelli. Unlike black piedra, white piedra can attack other haired areas of the body, not just the scalp. The disease has been diagnosed around the pubic area in both men and women. It’s unique symptoms are:
- creamy whitish nodules located at the base of the hair follicles
- Hair on the affected section of the scalp appears shorter and brittle
There are two main favorable factors for piedra infection:
- Applying plant oils on wet or semi-dry hair
- High humidity
How is Piedra Diagnosed?
Under black piedra, diagnosis is considered positive if brown spores are found in the hair. Mature nodules have eight visible ascopores characterized by presence of a flagellum at each tip.
On the other hand, a positive diagnosis for white piedra is confirmed if the hair contains groups of spores located on the affected area of the scalp. The spores can have varying sizes.