Indoor allergens are measured in several different ways, including detectability in settled dust, concentration, floor-area loading, reported dampness and health associations. The figures below cover U.S. homes, inner-city housing, a 13-country European cohort and EU-27 survey data; study periods are stated where the supplied sources identify them.
Key Indoor Allergen Statistics
The most broadly useful indoor allergen statistics include:
- In the study sampling period, Alternaria antigen was measurable in 90% of dust samples from 777 U.S. homes permitting resident children.
- In the study sampling period, cat allergen was measurable in 87% of 775 analyzed household-dust samples from U.S. homes.
- In the study sampling period, dog antigen was measurable in 92% of 775 analyzed household-dust samples from U.S. homes.
- In the study sampling period, house-dust-mite allergen was measurable in 38% of 774 analyzed samples from U.S. homes.
- In the First National Survey of Lead and Allergens in Housing, dust-mite allergen was detectable in 84.2% of beds in U.S. homes permitting resident children.
- In that national housing survey, 46.2% of U.S. homes had bed-dust mite allergen at or above 2.0 micrograms per gram.
- In that national housing survey, 24.2% of U.S. homes had bed-dust mite allergen at or above 10.0 micrograms per gram.
- During the study sampling period, visible mold or water damage was reported or observed in 57% of 777 U.S. homes.
- During the study sampling period, cats were present in 19.7% and dogs in 31.1% of 777 U.S. homes.
- During the study sampling period, more than 90% of 777 U.S. homes had carpet or an area rug covering floors.
- From 2019 to 2023, the EU-27 population living in a dwelling with dampness rose from 12.7% to 15.5%.
- In the latest period reported by the EEA, reported dwelling dampness ranged from 6.3% in Switzerland to 34.7% in Türkiye among the listed non-EU countries.
- A national housing estimate cited in a CDC-reviewed source found detectable mouse allergen in 82% of U.S. dwellings.
- The same cited national estimate found detectable cockroach allergen in 63% of U.S. dwellings.
- In a 608-home U.S. inner-city sample, 49% reported mouse problems during the previous year.
- In the WHO review of published epidemiology, current asthma associated with residential dampness factors had an odds ratio of 1.6 (95% CI 1.3–1.9).
- In a 9-year ECRHS follow-up of 7,104 adults in 13 countries, baseline water damage was associated with new asthma at a relative risk of 1.46 (95% CI 1.09–1.94).
- In an 18-home Boston pilot, integrated pest management reduced kitchen mouse allergen by 78.8% after 5 months, while controls increased 319%.
Contents
- Indoor allergen prevalence in household dust
- Dust-mite allergen statistics
- Cat and dog allergen data
- Mold, Alternaria and dampness trends
- Cockroach, mouse and pest allergen statistics
- Indoor allergens and respiratory outcomes
Indoor Allergen Prevalence in Household Dust
The 777-home U.S. study measured antigens in dust from a child’s primary activity room. These results describe sampled homes and assay detectability, not current national prevalence or clinical sensitization.
| Allergen or characteristic | Result | Population and period |
|---|---|---|
| Alternaria antigen | 90% measurable | 777 U.S. homes permitting resident children; study sampling period |
| Cat allergen | 87% measurable | 775 analyzed household-dust samples; study sampling period |
| Dog antigen | 92% measurable | 775 analyzed household-dust samples; study sampling period |
| House-dust-mite allergen | 38% measurable | 774 analyzed samples; study sampling period |
| Cockroach allergen | 14% measurable | 775 analyzed samples; study sampling period |
Source: The effect of home characteristics on dust antigen concentrations and loads in homes. Detection depended on the sampled room, assay threshold and collection method; dog antigen is not identical to clinical allergy.
The same study found cats in 19.7% of the 777 homes and dogs in 31.1%. More than 90% had carpet or an area rug, while visible mold or water damage was reported or observed in 57%; those housing characteristics do not by themselves quantify allergen exposure.
Only 10% of homes with visible mold damage had Alternaria spores detected on the damaged surface. Surface tape sampling does not measure all indoor fungal exposure, so this result should not be treated as the share of damaged homes with no mold-related exposure.
Dust-Mite Allergen Statistics in Beds and Bedrooms
National bed-dust data provide a different view from room-dust detectability. The First National Survey of Lead and Allergens in Housing covered permanently occupied, noninstitutional U.S. homes permitting resident children, and its thresholds are concentration cut points rather than diagnoses.
| Bed-dust measure | Share of U.S. homes or beds | Period and definition |
|---|---|---|
| Allergen detectable | 84.2% of beds | First National Survey of Lead and Allergens in Housing |
| At least 2.0 micrograms/g | 46.2% of homes | Bed-dust concentration threshold |
| At least 10.0 micrograms/g | 24.2% of homes | Bed-dust concentration threshold |
Source: House dust mite allergen in US beds: results from the First National Survey of Lead and Allergens in Housing. Detectability means at or above the assay detection limit and does not necessarily mean clinically important exposure.
In the 777-home study, the geometric mean Der f 1 concentration was 0.5 micrograms/g dust, with an interquartile range of 0.1 to 0.9 micrograms/g. The geometric mean Der f 1 loading was 0.2 micrograms/m2 of sampled floor area, with an interquartile range of 0.04 to 0.5 micrograms/m2.
A separate survey of 158 houses reported mean Der p 1 concentrations of 1.9 micrograms/g in living-room dust, 1.7 micrograms/g in bedroom dust and 2.0 micrograms/g in mattress dust. Concentrations above 10 micrograms/g occurred in 25% of living rooms, 25% of mattresses and more than 30% of bedrooms; these are survey estimates from the period reported in the practice parameter, not current national estimates.
Source: Environmental assessment and exposure control of dust mites: a practice parameter. Concentration and area loading are different measures and should not be interchanged.
Cat and Dog Indoor Allergen Data
Pet-related measurements varied sharply with ownership, but the study measured settled dust rather than personal airborne exposure. The following geometric means describe sampled household dust during the study sampling period.
| Household characteristic | Cat Fel d 1 | Dog antigen |
|---|---|---|
| No corresponding pet | 0.8 micrograms/g dust | 11.0 micrograms/g dust |
| One pet | 48.4 micrograms/g with one cat | 122.1 micrograms/g with one dog |
| Two or more pets | 108.1 micrograms/g with two or more cats | 157.4 micrograms/g with two or more dogs |
Source: The effect of home characteristics on dust antigen concentrations and loads in homes. The observational subgroups do not establish a causal increment per animal.
Across all sampled homes, the geometric mean Fel d 1 concentration was 2.0 micrograms/g dust, with an interquartile range of 0.3 to 9.2 micrograms/g; Fel d 1 loading averaged 0.6 micrograms/m2. With one cat, loading was 14.9 micrograms/m2, and with two or more cats it was 36.4 micrograms/m2, compared with 0.3 micrograms/m2 without a cat.
Dog antigen loading was 35.1 micrograms/m2 with one dog and 78.0 micrograms/m2 with two or more dogs, versus 3.4 micrograms/m2 without a dog. Loading is area-normalized settled dust, not inhaled dose or airborne concentration.
Mold, Alternaria and Indoor Dampness Trends
Alternaria was measurable in 90% of the 777-home study’s dust samples. Its geometric mean concentration was 47.3 micrograms/g dust, with an interquartile range of 25.5 to 79.2 micrograms/g; geometric mean loading was 14.8 micrograms/m2, with an interquartile range of 5.2 to 43.0 micrograms/m2.
Source: The effect of home characteristics on dust antigen concentrations and loads in homes. Settled-dust antigen is not a direct measure of airborne spore concentration or breathing-zone exposure.
The European Environment Agency reported a change in self-reported dwelling dampness across the EU-27:
| Geography | Dampness measure | Period |
|---|---|---|
| EU-27 | 12.7% of the total population | 2019 |
| EU-27 | 15.5% of the total population | 2023 |
| Switzerland | 6.3% of the population | Latest period reported by EEA |
| Türkiye | 34.7% of the population | Latest period reported by EEA |
Source: Indoor environment: mould and dampness. The EU-SILC indicator is self-reported dwelling dampness, not measured mold or allergen concentration; the non-EU comparison uses the EEA’s cited indicator.
Cockroach, Mouse and Other Pest Allergen Statistics
The 777-home study found measurable cockroach allergen in 14% of 775 analyzed samples. Its geometric mean Bla g 1 concentration was 0.8 IU/g dust, with an interquartile range of 0.4 to 0.9 IU/g, and geometric mean loading was 0.2 IU/m2.
Source: The effect of home characteristics on dust antigen concentrations and loads in homes. Most samples were near or below the assay detection range, and loading is not airborne concentration.
A later CDC-reviewed source cited national estimates of detectable mouse allergen in 82% of U.S. dwellings and detectable cockroach allergen in 63%. These percentages are reported through that later source summarizing the primary national housing survey; detection does not establish symptoms or clinical sensitization.
Source: National prevalence and exposure risk for cockroach allergen in U.S. households.
In the National Cooperative Inner-City Asthma Study, 49% of 608 U.S. inner-city homes reported mouse problems during the previous year, while 29% had mouse evidence in at least one room on inspection. Reported problems were self-reported, and inspection evidence was not a quantitative allergen concentration.
Indoor Allergen Exposure, Respiratory Outcomes and Reduction Results
Indoor allergen detection, dampness and respiratory outcomes are related but distinct measures. WHO’s quantitative synthesis found odds ratios from 1.34 to 1.75 across six dampness-related respiratory outcome categories and summarized several outcomes as approximately 30% to 50% increases; these were pooled associations from heterogeneous, often qualitative indicators.
Source: Health effects associated with dampness and mould: WHO Guidelines for Indoor Air Quality.
WHO reported an odds ratio of 1.6 (95% CI 1.3–1.9) for current asthma associated with dampness factors. It also reported a conditional U.S. estimate that residential dampness and mold accounted for 21% of asthma cases, plus an estimated annual U.S. cost of $3.5 billion if the associations were causal; neither is an observed case count or spending total.
In the 9-year ECRHS I–II follow-up of 7,104 adults in 13 countries, baseline water damage was associated with new asthma at a relative risk of 1.46 (95% CI 1.09–1.94). Baseline indoor mold was associated with new asthma at a relative risk of 1.30 (95% CI 1.00–1.68); the confidence interval borders 1.0, and exposure was not a standardized airborne allergen measurement.
Source: Mould and dampness in dwelling places, and onset of asthma: the population-based cohort ECRHS.
Measured intervention results are narrower than general cleaning claims. In an 18-home randomized Boston pilot involving children with asthma, integrated pest management reduced mouse allergen by 78.8% in kitchens after 5 months and by 77.3% in bedrooms; control homes increased 319% in kitchens and 358% in bedrooms.
Source: Environmental intervention reduces mouse allergen levels in homes of Boston inner-city children with asthma. The pilot included 12 intervention and 6 control homes and combined pest exclusion, cleaning, vacuuming, pesticides and traps, so its reduction cannot be attributed to vacuuming alone.