Triage · mattress inspection

You found something on the mattress. Here's the routine.

Don't try to brush it off, vacuum it up and forget it. Identify it first, what you do next depends entirely on what it is.

Right now (10 minutes)

Take a photo with macro focus or a phone camera close-up. Useful for AI ID (ChatGPT, Claude, Gemini all do this reasonably well) and for a pest professional later if needed.
Don't disturb the area yet. If it's a bed bug aggregation, fleeing bugs scatter into the wall void and a future treatment gets harder.
Strip the bedding. Sheets, mattress pad, pillow protectors. Bag them, seal the bag, take it directly to the laundry (60°C wash + 45 min high-heat dry).
Inspect systematically. The next section walks through it.

With a flashlight, go through these in order. Most positive findings are at #1 and #2; the rest are checks to rule out a spread.

Mattress seams, head end first. Lift a corner. Run the flashlight along every seam, piping and welt. Watch for live bugs (5-7mm, reddish-brown), fecal spots (pinhead black dots), eggs (1mm white clusters) or shed casings (translucent amber).
The mattress label. Classic harborage. Lift the label tag, look behind and around the stitching.
Box spring fabric. Especially the underside. If you can flip it, do it.
Bed frame joints and screw holes. Corner joints, headboard mounting points, slat-to-rail connections.
Behind a padded headboard. Lift it off the wall if it's hung. The fabric back is a major hidden harborage in hotels.
Nightstand drawer corners and behind it.
Outlet plates within a meter of the bed. Power off at the breaker, remove the cover plate, look inside with the flashlight.

Live bug, oval, ~5-7mm, reddish-brown: Almost certainly an adult bed bug. Cross-check with what bed bugs look like for lookalikes (bat bugs, carpet beetle larvae).
Cluster of small dark dots that smear when wiped: Fecal staining. Strong evidence of bed bugs. Color is from digested blood.
Translucent amber husk: Shed nymph casing. Diagnostic, only bed bugs and bat bugs leave these. Confirms an established population.
White rice-grain shaped specks in a cluster: Bed bug eggs. Confirms an actively breeding population.
Single live bug but no fecal spots, casings or eggs: Possibly a recent introduction, possibly a stray. Treat seriously, interceptors under bed legs, encasement on mattress, check again in 2 weeks.

Confirmed bed bugs, single-room apartment, small infestation: structured DIY protocol. See DIY treatment without making it worse.
Confirmed bed bugs, multi-unit building: tell the landlord. Professional building-wide treatment is the only thing that works long-term.
Confirmed bed bugs, established (multiple aggregations, heavy fecal staining): professional thermal remediation. DIY at this scale takes months and often fails.
Lookalike or single ambiguous finding: encase the mattress, put interceptors under bed legs, monitor for 4 weeks before deciding.