Localized hypertrichosis after infectious rash or “HAIR”, has been reported following a variety of skin and soft tissue infections (SSTIs), including sites of previous septic thrombophlebitis, cellulitis and olecranon bursitis. 1,2 A similar phenomenon has also been described in infants with recent chicken pox, as well non-infectious skin conditions arising from repeated irritation, friction, burns, excoriated insect bites, and fractures with cast application.1,2
Although heat and hyperemia have been implicated as growth stimulants for the hair follicle, 3 the exact mechanism of this intriguing phenomenon is unclear. It is possible that the sustained inflammatory process associated with chronic or more severe SSTIs leads to protracted stimulation of certain growth receptors in the human hair follicles (eg, transient vanilloid receptor-1) through heat and inflammation, as observed in mice in vivo.4
Aside from its possibly undesirable esthetic effects, localized HAIR appears to have no adverse health consequences, is reversible, and should require no further evaluation.
Note: 2 of the publications cited were written by the author of this post.
- Manian, FA. Localized hypertrichosis after infectious rash in adults. JAAD Case Reports 2015; 1:106-7. https://www.jaadcasereports.org/article/S2352-5126(15)00051-X/pdf
- Manian, FA. Localized hypertrichosis after infectious rash (“HAIR”) in adults: a report of 5 cases. Open Forum Infect Dis 2014;1 (Suppl 1):S195-S195. http://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC5782143&blobtype=pdf
- Leung AK, Kiefer GN. Localized acquired hypertrichosis associated with fracture and cast application. J Natl Med Assoc 1989;81:65-7. https://www.ncbi.nlm.nih.gov/pubmed/2724357
- Bodo E, Biro T, Telek A, et al. A hot new twist to hair biology; involvement of vanilloid receptor-1 (VR1/TRPV1) signaling in human hair growth control. Am J Pathol 1005;166:985-8. https://www.sciencedirect.com/science/article/pii/S0002944010623206
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