Mysophilia

Mysophilia is arousal from dirtiness — soiled, filthy, or 'used' things, especially items marked by bodily fluids or the body's natural funk. Worn, unwashed underwear is the classic example, but it's a broad paraphilia that can extend to sweat, dirt, grime, or anything unclean. The turn-on is precisely the taboo of the unhygienic — the intimacy and rawness of another person's scent and traces. It overlaps with scent fetishes (olfactophilia), used-panty fetish, and sweat play. It ranges from a mild love of a partner's worn shirt to a dedicated dirt fetish.

The appeal is raw, unfiltered intimacy — the funk, scent, and traces of a real body feel far more personal and animal than anything clean and sanitized. The taboo of desiring the 'dirty' adds its own transgressive charge.

It might mean savoring a partner's worn, unwashed underwear or clothing, getting off on sweat and body odor, or working deliberately 'dirty' or messy elements into sex. Worn-item exchange (in person or bought) is a common expression.

Mostly low-risk, but 'dirty' bodily materials can carry bacteria — avoid anything that could cause infection near mucous membranes or broken skin, and be cautious with actual filth or unknown substances. Worn items from strangers carry the usual hygiene caveats.