Short answer
A fishy smell is the signature of amines; PubChem describes trimethylamine's odor as fishy and ammonia-like. In a mattress, amines form as organic soil such as body fluids, urine or spills breaks down over time, and warmth and humidity make the smell stronger. Enzyme treatment breaks down that organic soil, and dry vapor steam and HEPA vacuuming finish the job.
Book your mattress cleaning
Regular price $249, Fall 2026 promotion price $199first mattress, any size · Fall 2026 promotion
HEPA vacuuming, enzyme treatment for organic odor, dry vapor steam and UV-C. We recommend cleaning twice a year.
Few smells send people to a search bar faster than a fishy bed. The good news: it has a specific chemical cause.
What makes a mattress smell fishy?
The fish smell comes from a family of compounds called amines. PubChem records trimethylamine's odor as "fishy, amine odor" and describes it as fish-like at low concentrations, changing to ammonia-like at higher ones (PubChem). Amines are released as protein-rich organic soil breaks down, so a fishy mattress usually means body fluids, urine or food and drink spills have been sitting in the cover or foam.
Why does it smell worse at night or in summer?
Warmth and humidity help odor compounds lift out of the fabric. Your body heat does the same thing every night, which is why the smell can seem strongest once you've been in bed a while.
Fishy vs ammonia vs sour
- Fishy: amines from breaking-down organic soil.
- Sharp ammonia: usually urine; see the urine and odor guide and why urine odor comes back.
- Sour or cheesy: sweat and skin oil (sour mattress smell).
How to remove it
Fragrance won't hold against amines for long. The source has to come out: we map the area by smell, dry-vacuum with HEPA, apply enzyme sparingly to break down the organic soil, then make low-moisture dry vapor steam passes (enzyme and steam together). If the smell is coming from an electric adjustable base or heated pad instead of the mattress, unplug it and have it checked.
How we get the smell out
This section is our view. Every Sleep Sanitation visit starts with a nose-and-eyes inspection to find where the odor actually lives, then HEPA vacuuming, enzyme treatment on organic odor, low-moisture dry vapor steam from our Italian-made Vapor Clean machines, UV-C light treatment and a moisture check before we leave. That sequence goes after the source of the smell instead of covering it with fragrance. The first mattress is $199 Fall 2026 special (regularly $249), any size. We recommend cleaning every mattress twice a year so odor never gets a head start. Not sure what your bed needs? Take the 60-second mattress quiz, or schedule your cleaning. Call or text (402) 512-5658, or email info@sleepsanitation.com.
Changelog
- 24 October 2026: First published. Sources accessed on this date.
Sources
- Trimethylamine, compound summary · PubChem (NIH)
- Microbial Origins of Body Odor (December 2021) · American Society for Microbiology
Last reviewed October 24, 2026. Manufacturer specifications and care instructions change; check the current version for your exact model. This page is general information, not medical advice. How we source and check pages: editorial standards.