Indoor environment factor · measured in EU/m³ or EU/mg of dust
Endotoxin
Part of: Bioaerosols
Also: lipopolysaccharide, LPS
A component of the outer membrane of Gram-negative bacteria, carried indoors on dust particles rather than as a gas. It is measured in settled dust or airborne dust and is one of the few biological exposures with an established laboratory assay, which is why it appears in studies where mould and bacteria in general do not.
Why it matters indoors
Endotoxin is the part of the microbial world that can be counted reliably. Mould and bacteria indoors are hard to quantify — species differ, sampling differs, and results rarely compare between studies. Endotoxin has a standard assay, so it became the practical proxy for bacterial exposure in homes, and much of what is known about bacteria and indoor health rests on it.
What the evidence looks like
The picture is two-sided rather than simple. Bedroom concentrations have been linked to a higher risk of atopic dermatitis in preschool children, while exposure in early life on farms is repeatedly associated with less allergic disease. Reading either half alone gives the wrong answer; the honest summary is that endotoxin is not a contaminant to eliminate but an exposure whose effect depends on when and how much.
What the studies report
| Linked to | Effect | Population | Study design | Source | Checked |
|---|---|---|---|---|---|
| Asthma | OR 0.39 (0.15–1.01) per 1 quartile | — · home | gene-environment interaction analysis within two birth cohorts: early-life endotoxin exposure in house dust related to asthma and eczema by age 6, tested for interaction with candidate single nucleotide polymorphisms | F-1685 Effects of endotoxin exposure on childhood asthma risk are m… (2011) | machine |
| Atopic dermatitis (eczema) | OR 1.31 (1.03–1.67) | preschool children · home | cross-sectional measurement in 120 households of a birth cohort | F-0008 Huang Effects of indoor air quality and home environmental charact… (2023) | machine |
Each row is one Finding — a sentence as printed in one study, recorded with its page in the Coridum Knowledge Base. Follow the Finding number for the exact wording and the citation. Checked says who verified the row: machine means every automatic check passed and the surrounding text was read; person means someone read the sentence in the document. Rows are re-checked by a person over time. The studies are curated in the Coridum Knowledge Base; the reading of them together is a Claim, shown separately.
Identifiers
- MeSH
- D004731
Frequently asked questions
Where does indoor endotoxin come from?
Gram-negative bacteria that live wherever there is moisture and organic material: damp surfaces, humidifiers, kitchen waste, pets and their bedding, and outdoor air in agricultural areas. It is carried indoors on dust, so it accumulates in mattresses, carpets and soft furnishings.
Is endotoxin always harmful?
No, and this is one of the genuinely unresolved questions in the field. Higher bedroom concentrations have been associated with atopic dermatitis and with asthma symptoms, while early-life exposure in farming environments has been associated with less allergy — the so-called protective effect. The dose, the timing and the age at exposure all appear to matter.
Can a sensor measure it?
No. Endotoxin is quantified in a laboratory from dust collected in the room, with an assay reported in endotoxin units. No continuous indoor sensor measures it, which is why studies use dust sampling campaigns rather than monitoring.
In the literature
- Huang Effects of indoor air quality and home environmental characteristics on allergic diseases among preschool children in the Greater Taipei Area (2023). doi:10.1016/j.scitotenv.2023.165392 CKB 0539
- Seasonal variations of indoor microbial exposures and their relation to temperature and… (2012). doi:10.1128/AEM.02069-12 CKB 0477
- Concentration and determinants of molds and allergens in indoor air and house dust of French dwellings (2015). The Science of the total environment. doi:10.1016/j.scitotenv.2015.06.039 CKB 0479
Studies in the Coridum Knowledge Base in which this term is used. The definition follows standard usage in WHO, ISO and textbook sources; it is not quoted from these papers.
CKB = document number in the Coridum Knowledge Base, our curated library of peer-reviewed studies. Follow the DOI for the original paper.
Cite this page
Coridum Research. Endotoxin. Coridum Knowledge G-0092, 16 September 2026. https://coridum.com/k/G-0092/