Chemical treatment of carpets to reduce allergen: comparison of the effects of tannic acid and other treatments on proteins derived from dust mites and cats.

BACKGROUND Several chemical treatments have been recommended for reducing mite and other allergen levels in carpets, including the protein-denaturing agent tannic acid (TA). OBJECTIVE We evaluated the efficacy of TA and other treatments on mite and cat allergens in carpets within houses. The effects of TA were assessed on Der p 1 and Der f 1, on group II mite allergens, and on the major cat allergen Fel d 1. METHOD Carpet treatments tested were benzyl benzoate moist powder, a 3% TA spray, and two carpet cleaners (Host and Capture). Carpets were treated twice and dust samples collected on a biweekly basis for 8 weeks: these samples were extracted in saline solution alone. Additional studies evaluated the effects of TA on 17 carpets. Carpets were treated twice (on days 0 and 28) and samples collected on days 0, 1, 7, 14, 28, and 42. Eighteen carpets were untreated controls. Dust samples were extracted separately in both saline solution and in the presence of 5% bovine serum albumin. RESULTS Benzyl benzoate and the two carpet cleaners reduced group 1 dust mite allergen concentrations in carpet dust. In addition, benzyl benzoate and TA reduced airborne group 1 mite allergens by more than 64%. Further studies showed that, in keeping with in vitro studies, TA inhibited the assay and bovine serum albumin abrogated this effect. Significant reductions after treatment occurred only for Der f 1 and group 2 dust mite allergens (p = 0.005 and p = 0.035, respectively). However, for all mite allergens the percentage changes after treatment were significant when compared with untreated carpets (p < 0.005 for Der f 1 and group 2 mite, p < 0.02 for Der p 1) but not for cat allergen (p > 0.3). The results suggested that repeated application of TA was necessary to maintain reduced allergen concentrations. CONCLUSION Carpet treatments can reduce mite-derived allergen levels in airborne and carpet dust. However, the effects do not appear to be maintained for long periods, are not dramatic, and are different for different allergens.