What it actually is
Smegma is a mix of shed skin cells, natural oils, and moisture that the body produces around the genitals — it's not dirt, and it's not caused by not washing. On a penis, it collects under the foreskin, in the space between the foreskin and the glans. On a vulva, the equivalent buildup collects around the clitoral hood and between the inner labia. Both are the same basic process: skin cells naturally shed and mix with oil glands' output in a warm, somewhat enclosed area, faster than in most other places on the body.
Everyone with a penis or a vulva produces some amount of it, including people who shower every day. Uncircumcised penises typically produce more of it than circumcised ones, simply because the foreskin creates more enclosed space for it to collect in — that's an anatomical difference, not a hygiene difference.
How to clean it
Gently retract the foreskin, or separate the labia and clitoral hood, during a regular shower and rinse the area with warm water. For a lot of people, plain water is genuinely enough — some dermatologists specifically caution against using soap directly on the glans, since it can strip natural oils and cause irritation or dryness for some people. If soap is used, a mild, fragrance-free option applied around rather than directly on the most sensitive skin is the safer choice. Dry the area fully afterward; trapped moisture is a bigger factor in buildup accumulating quickly than skipping a day of washing is.
When it's actually a problem
Smegma itself isn't the problem — buildup left unaddressed for a long time is what can start to cause irritation, odor, or contribute to infections like balanitis (inflammation of the glans and foreskin), particularly if the foreskin is tight or difficult to retract fully. A few signs it's worth seeing a doctor rather than just adjusting your routine: pain or swelling, odor that doesn't resolve with normal rinsing, redness or a rash, or any difficulty pulling the foreskin back that wasn't there before. That last one specifically — a foreskin that's becoming harder to retract over time — can indicate phimosis, which is a real medical condition worth getting checked rather than working around.
Why the shame around this doesn't match the biology
Because it's rarely discussed openly, a lot of people find out about smegma for the first time through an alarmed internet search, which tends to frame it as something wrong rather than something universal. It's genuinely one of the most normal bodily processes there is — closer to earwax than to a hygiene failure. Routine washing, not any special product or ritual, is all that most people need.