Chemical treatment of carpets to reduce allergen: A detailed study of the effects of tannic acid on indoor allergens

Abstract

Tannic acid (TA), a protein-denaturing agent, has been reported to reduce allergen levels in house dust and is marketed for that purpose as 1% and 3% solutions. We investigated the effects of TA on dust allergens by using monoclonal antibody-based ELISAs for mite (Der p I, Der f I, and group II) and cat (Fel d I) allergens. Initial studies confirmed that TA reduced allergen levels in carpet dust. However, when dust samples from treated carpets are extracted in saline solution, residual TA redissolves and may interfere with the assessment of allergens. In the laboratory, concentrations of TA as low as 0.1% inhibited the assays, but this effect may be prevented by addition of 5% bovine serum albumin (BSA). After treatment of dust samples in the laboratory with 3% TA, the apparent reductions in Der p I and Der f I levels were 89% and 96%, respectively, but when the samples were extracted in 5% BSA the reductions were 74% and 92%. Similar effects were seen with dust samples from carpets treated with TA. In an extreme case in which a carpet had been repeatedly treated with TA, the apparent concentration of Der p I was < 0.05 μg/gm without BSA and 2.1 and 8.4 μg/gm when extracted in the presence of 1% and 5% BSA, respectively. Our testing of the ability of TA to denature Fel d I demonstrated an 80% reduction in allergen, but only in samples with an initial concentration of less than 200 μg Fel d I/gm dust. In samples with high levels of Fel d I (≈1 mg/gm) TA had little effect. The interpretation of this was that Fel d I itself could block the effects of TA. In keeping with this, Fel d I inhibited the effect of TA on Der p I. The results confirmed the profound denaturing effects of TA, but demonstrated that high levels of protein blocked the effect of TA on dust allergens. In addition, without added protein, residual TA in dust samples could interfere with the assay of allergens in vitro. (J ALLERGY CLIN IMMUNOL 1994;94:19-26.)