Blackhead

A blackhead is an open comedone. A pore fills with a mixture of sebum and dead keratinocytes, the plug reaches the surface, and its top oxidises on contact with air. That oxidation is what makes it dark — not dirt, and not a lack of washing. Scrubbing harder cannot remove something that is not on the surface, and treating a blackhead as a hygiene failure leads to exactly the over-cleansing that makes the skin produce more oil.

The distinction that matters most is between blackheads and sebaceous filaments, because the two look similar and respond to completely different things. Blackheads are irregular, occur where oil and dead cells accumulate, and can be resolved. Sebaceous filaments are the small, uniform greyish dots that line the nose and cheeks in near-identical spacing; they are a normal structure that channels sebum out of the pore, they exist on everyone, and no product removes them permanently.

What actually clears blackheads is keeping the pore from re-plugging. Salicylic acid is the first choice because it is oil-soluble and reaches inside the pore; retinoids work more slowly but more durably by normalising how cells shed. Physical extraction empties a pore for a week or two and does nothing about the process that filled it. Pore strips remove the very top of the plug and leave the rest.