Doctors in Brazil were surprised to find the cause of a man’s niggling eight-hour foot pain – a tiny hair.

The 35-year-old patient presented at an emergency department in Sao Paulo with pain in his right heel that worsened while walking, according to a report in the Journal of Emergency Medicine released June 20.

An initial examination couldn’t find anything wrong, but on re-evaluation a doctor spotted a hair in his heel.

“Dermoscopy with a handheld dermatoscope showed a five millimetre hair penetrating the skin,” the report authors wrote.

“A hair measuring 10 millimetres was removed with tweezers and pain relief was immediate.”

The rare condition is called cutaneous pili migrans (CPM), the study authors explained.

“A hair penetrates into the superficial layer of the stratum corneum (outer layer of skin) and thence it can migrate due to foot movements in a creeping pattern,” they wrote.

Usually CPM has no symptoms, but sometimes it causes mild pain.

The doctors speculated that the patient had stood on the hair shaft in his bare feet when it became embedded in the outer layer of skin, stimulating the nerve endings.

The study explains that Asian hair has a larger diameter and is firmer and straighter than African or Caucasian hair, making it the most common hair seen in cases of CPM.

“The diagnosis is essentially clinical and complete removal of the hair is required for cure,” the study states.

“Physicians should be aware of this unusual foreign body reaction in patients with discomfort on the soles of the feet.”