A 17-year-old girl asks why her blackheads are black despite regular face washing. The pigment responsible for the dark colour of an open comedone is:
- A Haemosiderin from microhaemorrhage
- B Deposited environmental dust and soot
- C Melanin oxidised by air exposure ✓
- D Pigment produced by Cutibacterium acnes
Correct answer: C. Melanin oxidised by air exposure
Explanation
The black colour of an open comedone results from oxidation of melanin (with contributions from sebum lipids) as the keratin plug contacts air at the follicular orifice. It is not dirt, which is a common patient misconception worth addressing. A. acnes produces porphyrins that fluoresce coral-red under Wood lamp but does not produce black pigment. Haemosiderin causes brown macules in stasis dermatitis, not comedones.
Reference: Rook's Textbook of Dermatology, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.