Keratosis pilaris appears as horny plugs blocking the follicles across the outer parts of the upper arms and the thighs, with the appearance of goosepimples but feeling slightly coarse. There is usually no inflammation around each follicle, or infection.4

Comedones, a common feature of acne, are blocked hair follicles caused by a proliferation of sebaceous gland cells secreting more sebum, but not considered to be inflamed.6

Blackheads are open comedones which will empty if squeezed, with the dark colour coming from melanin in the hair follicle. Whiteheads are uninflamed closed comedones, with no channel to let the build-up escape when squeezed.6,7,8

Moderate to severe cases of acne will move beyond comedones to include:7

·       papules – inflamed closed bumps and sore to the touch

·       pustules – inflamed and open, with a tip of white/cream pus in the centre

·       nodules – larger and firmer non-draining lumps which can become painful

·       cysts – large pus-filled lumps similar to boils.

Comedones are not a typical feature of rosacea: after the initial skin reddening or erythema, spots and blemishes will develop, but these tend to be papules, pustules and general inflammation. That said, rosacea can occur along with acne which may be comedonal.9,10