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Carpets may not be the culprit

Study results suggest that carpeting helps to keep allergen levels lower compared to that of solid flooring

ORLANDO, Fla. — For children with asthma, physicians generally advise parents to remove wall-to-wall carpeting in their homes as a way to limit allergen exposure. However, initial findings of a study presented during the American Academy of Allergy, Asthma & Immunology 2012 Annual Meeting question that rationale.

Researchers from Ireland reported that results of their study raise significant doubts about the assumed relationship between surface and airborne allergen levels.

“We measured high levels of cat and dust mite allergen in the air of a room with a hard floor as opposed to carpets,” said Angela Southey, PhD, technical manager at Airmid Health Group in Dublin, Ireland, where the testing was conducted. “Our findings are actually the opposite to what physicians are recommending currently. However, the carpets must be regularly cleaned through dry vacuuming and hot water extraction.”

Southey also said pile height and carpet construction should be taken into consideration.

“A hard-wearing carpet would be recommended, of medium pile height because it traps more allergen than a lower pile height carpet,” she said.

Six different carpets and one hard floor were each laid in an AC-1 chamber under controlled conditions. Southey and colleagues aerosolized Allergen Test Dust, of known composition into the chamber. They then measured serial airborne particle counts, surface and airborne allergen measurements (augmented enzyme-linked immunosorbent assay) during natural decay, room disturbance and vacuuming.

After allergen test dust introduction and during room disturbance, significantly greater airborne particle counts/m3, for respirable particles, were identified with the hard floor compared with Carpet 3 (P<.01) and Carpet 2 (P<.05).

Airborne dust mite allergen measurements were also greater during room disturbance for the hard floor (74.7 pg/L) than for Carpets 3 and 2 (55.5 pg/L and 43.2 pg/L, respectively). In addition, according to Southey, vacuuming exaggerated these differences, with the hard floor having greater airborne dust mite allergen levels (252.7 pg/L) compared with Carpet 3 (55.5 pg/L) and Carpet 2 (212 pg/L).

In contrast, surface allergen measurements (microgram per square meter) for the hard floor were reduced by vacuuming (14.4 pg/L to 0.2 pg/L) while only moderately reduced for Carpet 3 (24.0 pg/L to 11.4 pg/L) and Carpet 2 (22.5 pg/L to 8.3 pg/L).

Relevant particle counts and airborne allergen levels remained higher for the hard floor than for the carpets during vacuuming. However, Southey said repeated vacuuming resulted in reduced airborne particles for hard floor and carpet 2, whereas carpet 3 was low throughout.

“In our study, the carpets differed greatly in their ability to retain allergens she said. Carpet construction, density, age and cleaning regime should be considered when advising parents about different floor types. “If the carpet becomes very worn, it would be recommended to change the carpet because although worn carpet may hold onto allergen it could become saturated.”

Southey said tests have shown that regular cleaning should be performed to remove allergens from carpeting and to prevent resuspension and inhalation of particles carrying allergens such as those from dust mites and cats. Additional studies are planned to further investigate this theory, she said.

Disclosure: Dr. Southey is an employee of Airmid Healthgroup Ltd.

For more information:

• Mitchell B. #341. Presented at: the AAAAI 2012 Annual Meeting; March 2-6, 2012; Orlando, Fla.