The smell is hard to mistake: sweet, rotten and strongest in one room or one corner. It often shows up a few days after rodent noises stop, and it tends to be worse on hot days. In most cases a rat or mouse has died somewhere you can't see, inside a wall, under the floor, in the attic or in a crawlspace.
Signs it's a dead rodent
- The smell is strongest in one spot and gets weaker as you walk away from it.
- It's worse in warm weather, in the afternoon, or when the heating or air conditioning runs.
- Flies gather near one wall, a ceiling light, a vent or a window.
- A stain or damp patch appears on the ceiling or the wall in rare cases.
- The scratching stopped. You heard noises in the walls or attic, then silence, then the smell.
Why it happens
The most common cause is poison. A rodent eats the bait, then goes back to its nest inside the house and dies there. It's one reason most anticoagulant rat poisons are now banned for home use in California (see the California rat poison ban). Rodents can also die inside after getting trapped, or simply of old age in a nest in the attic or the walls.
Wait it out, or remove it?
The smell does fade on its own as the body dries out, but that usually takes weeks, longer for a rat than a mouse, and the heat in Los Angeles summers makes it stronger. Waiting also leaves the problem underneath in place: if one rodent got into the wall, others can too, and they may still be there.
How it's found and removed
- Tracing the smell. A technician follows it to the strongest point, checking the attic, crawlspace, vents and wall cavities, often without opening a wall.
- Removal. If the rodent can be reached from the attic or crawlspace, it's taken out from there. If it's sealed inside a finished wall, a small access hole may be needed, then patched.
- Cleanup. The spot and any soiled insulation are cleaned and disinfected. See attic cleanup.
- Finding the way in. The entry points are found and sealed so it doesn't happen again. See rodent exclusion.
If you find it yourself
The CDC's advice for handling a dead rodent:
- Wear rubber, latex or vinyl gloves.
- Spray the rodent and the area around it with a disinfectant or a bleach solution (1 part bleach to 10 parts water) and let it soak for about 5 minutes.
- Pick it up with a paper towel, seal it in a plastic bag, and put that in a second bag with any nesting material. Throw it out with the household trash.
- Disinfect the spot again, then wash your gloved hands, remove the gloves and wash your hands with soap and water.
What comes next
A dead rodent in a wall is proof that rodents have a way in. If you're still hearing noises, read noises in the attic at night, and for the usual entry points see how rats get into your house.
Get it looked at
Tell us where the smell is and we'll connect you with a state-registered pest control company that serves Los Angeles County. Start with attic cleanup, or call the number at the top of the page.
More guides
- How rats get into your house, and where to look
- Rats chewing your car wires: what's going on
- Mice in the walls: what the sounds mean and what to do
This guide is general information, not a substitute for an on-site inspection. SealWell is a referral service, not a contractor.
