Folliculitis or inflammation of the hair follicle can range from a mild irritation just under the surface (superficial folliculitis), to something more deep-seated and painful.

S. aureas is the most likely pathogen in many types of folliculitis, but others include:17,18

·       bacterial: Pseudomonas spp such as Pseudomonas aeruginosa (often from inadequately treated swimming pool water) and several Gram negative bacteria

·       fungi, yeasts and moulds: Trichophyton spp or Microsporum spp (usually tinea infections), Malassezia or Candida albicans (a possible cause of folliculitis barbae or shaving rash)

·       viruses: herpes simplex and herpes zoster in shingles.

Non-microbial causes include physical injury such as abrasion, ingrowing hairs, chemical irritation or occlusion (eg from paraffin-based ointments or dressings). Topical corticosteroid use and long-term antibiotic use may also trigger folliculitis.17,19,20

Folliculitis pus can therefore be sterile as a local immune response. In the case of shaving rash, if it is caused by ingrowing hairs and not infection this is pseudofolliculitis barbae.

A deep follicular infection will result in a boil or furuncle. A boil will swell into a large firm lump before usually coming to a head from which the pus can drain. This process can be speeded up applying a warm, moist compress to the developing boil for 10-20 minutes 3-4 times a day.21,22

If several follicles close together are affected, the resulting carbuncle may be 10cm wide with several exuding heads. A boil may also be accompanied by superficial folliculitis at the same time.

Folliculitis barbae is usually superficial, but if it gets hold more deeply into the follicles, the inflammatory reaction can lead to larger swellings, known as sycosis barbae. This occasionally leaves scarring.23,24