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.

The original paper calls it "a common morphological variant." A filament is not a lesion, but one of the shapes a sebaceous follicle normally takes. The same paper states that filaments should be distinguished 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.

When blackheads and sebaceous filaments are hard to tell apart, look at the 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. Measuring follicle density and sebum output together across facial sites, researchers found no correlation between the two (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.

The literature holds a different argument about the pigment in blackheads. A 1970 histochemical 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 electron-microscopy 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. The original paper recorded that the follicle refills within thirty days of expression (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.

Emptying a spot each month that refills each month is repetition, not maintenance. 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. Thirty days is the reference point.
• If only a few are dark and firm, don't push them out by hand. A cleanser with salicylic acid on the list, used at the evening wash and given thirty seconds before rinsing, does more than your fingers will.
• If the area is red or sore, or the count has been rising for months, have a dermatologist look at it before repeating another round of self-care. Not every dark spot on a nose is a pore.