A comedo (plural comedones) is a plugged follicular orifice.
- Open comedones (blackheads) are grey, orange, brown or black papules. The keratinous contents can be expressed or extracted.
- Closed comedones (whiteheads) are uninflamed skin-coloured papules. They must be punctured to remove their contents.
Skin lesions and conditions in which there are prominent comedones include:
- Acne, especially acne vulgaris and comedonal acne
- Hidradenitis suppurativa
- Solar (senile) comedones and Favre Racouchot syndrome
- Discoid lupus erythematosus
- Seborrhoeic keratosis (best seen on dermoscopy)
- Compound or dermal papillomatous melanocytic naevus or mole (best seen on dermoscopy)
- Comedone naevus
- Epidermal cyst (giant comedo)
- Dilated pore of Winer