Blackhead

A blackhead (medically known as an open comedo, plural comedones) is a yellow or blackish bump or plug on the skin, and usually found on the face or the back. Blackheads are one of the common findings in acne vulgaris. Contrary to the common belief that it is caused by poor hygiene, blackheads are caused by excess oils that have accumulated in the sebaceous gland's duct. The substance found in these bumps mostly consists of keratin and modified sebum (an oily secretion of the sebaceous gland), which darkens as it oxidizes. Clogged hair follicles, where blackheads often occur, reflect light irregularly to produce a blackhead's "black" hue. For this reason, the blockage might not necessarily look black when extracted from the pore, but may have a more yellow-brown colour as a result of its melanin content.