Sebaceous filaments or blackheads — which is it?

Most of the greyish dots packed across a nose are not blackheads. They are sebaceous filaments. The two were described as separate structures in a 1976 paper, and an emptied filament refills within thirty days (Plewig & Wolff, 1976). One is worth clearing and the other is simply there, so without the distinction you end up squeezing the same spots every month.

What is a sebaceous filament?

A sebaceous filament is a tube of ten to thirty layers of horny cells, holding sebum, bacteria, fragments of corneocytes and a single vellus hair (Plewig & Wolff, 1976). Sebaceous filaments are common in the centre of the face after puberty, especially on the sides of the nose, in people with active sebum and large pores.

A sebaceous filament is a normal shape a sebaceous follicle takes, not a skin condition. The original paper calls it "a common morphological variant." Filaments are also a separate structure from a microcomedo.

How is a sebaceous filament different from a blackhead?

A blackhead is an open comedone: the pore mouth plugged with keratin, its upper end dark, occurring one at a time. Sebaceous filaments sit evenly and densely across the whole nose, and run greyish or pale yellow.

If blackheads and sebaceous filaments are hard to tell apart, go by how they are spread. Evenly covering the nose points to filaments; a handful that are noticeably darker and raised points to comedones.

The nose does not stand out because it has more pores. Across facial sites, follicle density and sebum output showed no correlation (Pagnoni et al., 1994). What is visible is decided by what fills the pores, not by how many pores there are.

Why is a blackhead dark?

"Sebum oxidises on contact with air" is everywhere, but no primary study supporting it turned up. Nor did any study refuting it. So don’t scrub at the dark tip.

The literature holds a different argument about the pigment in blackheads. A 1970 study reported the predominant pigment as melanin: comedones from people with albinism carried none, and darker-skinned donors had darker comedones (Blair & Lewis, 1970). A 1974 paper explained the dark tip by melanocytes being confined to the superficial part of the follicle (Kaidbey, 1974).

Then a 1983 study found no melanosomes at all in open comedones, and concluded that melanin cannot be the source of the black colour (Zelickson & Mottaz, 1983). No later study settling the argument turned up. The honest answer is that nobody knows yet.

Does squeezing get rid of sebaceous filaments?

Sebaceous filaments do not go away. An emptied sebaceous filament refills its follicle within thirty days (Plewig & Wolff, 1976).

No primary study showing that pore strips change anything durably turned up either, and the claim that they take stratum corneum with them is not verified at that level either. If the skin reddens or tightens after a pore strip, though, that is skin irritation — ease off. How far oil cleansing gets continues in does oil cleansing actually remove blackheads.

In short: clear blackheads, leave sebaceous filaments

A blackhead is a blockage, so it is worth loosening. Dissolving keratin slowly beats pushing it out. It appears on an ingredient list as salicylic acid, and in Korea the strength sits in rinse-off formats — a leave-on cosmetic there holds 0.5% or less, for reasons set out in why exfoliating does not clear closed comedones. A sebaceous filament is a sign that a sebaceous follicle is working, and pushing at it leaves only irritation.

Don’t empty sebaceous filaments every month; leave them for one month and watch. Stop chasing a smooth nose for one month and the difference between what was always there and what irritation created becomes visible. Pore size itself is in large pores and blackheads.

One step today

• If the dots are spread evenly across the nose, rest the squeezing and the strips this month. An emptied filament refills within thirty days (Plewig & Wolff, 1976). If after thirty days the dots are still spread evenly, they are filaments. If the area turns red or sore, or the count rises in the meantime, see a dermatologist.
• If only a few are dark and firm, use a cleanser with salicylic acid on the list at your evening wash. Leaving it on for thirty seconds before rinsing is common practice; no trial has tested whether it reduces blackheads. Don't push them out by hand, and use it less often if it stings. If the count keeps rising for months, or a spot turns red and swollen, see a dermatologist.