Background: Cutaneous pili migrans is a rare condition in which the hair shaft penetrates the superficial layer of the skin and produces a creeping eruption mimicking the lesion of cutaneous larva migrans.
Methods: We report a 28-year-old Chinese man who presented with a painful and slow-moving black, linear eruption on the left sole after walking on a waterlogged street wearing slippers without socks.
Results: The lesion started at the anterior part of the foot near the external border, extending linearly along Langer's line towards the lateral side. It then turned in a U-shaped direction and moved across the foot to the other side, where it made a right angle and moved along the internal side of the foot. The lesion was reminiscent of cutaneous larva migrans. Walking made the line move more quickly. Physical examination showed that there was a broken epidermis at the probable entrance and a black thin line at the advancing end of the lesion. The black line was demonstrated to be a hair shaft with a sharp head by a shallow incision of the skin and examination under a microscope. After removal of the hair, the pain disappeared and the lesion diminished immediately, leaving slight pigmentation.
Conclusion: The broken epidermis may be one of the main reasons for the hair shaft entering the skin. The force of body motion caused movement, which was made easier by the sharp head of the hair shaft. Hair can produce an eruption reminiscent of cutaneous larva migrans.