Warming of feet elevates nasal mucosal surface temperature and reduces the early response to nasal challenge with allergen

Background: We have previously shown that hot, humid air partially reduces the early allergic response. Mechanisms for this effect have been suggested, but none has gained universal acceptance. The most likely explanations are a modification of mucosal temperature or a reduction in nasal secretion osmolality. Objective: We sought to investigate whether increasing the nasal mucosal surface temperature by immersing feet in warm water (WW) could decrease the immediate nasal response to challenge with allergen. Methods: We performed a randomized, 2-way crossover study on 14 subjects with seasonal allergic rhinitis outside of their allergy season. They immersed their feet in either WW (42°C) or room-temperature water (RW; 30°C) for 5 minutes before and during nasal challenge with diluent for the allergen extract, followed by 2 increasing doses of allergen. Results: There was a statistically significant increase in nasal mucosal temperature from baseline after warming of feet (WW, 1.9 ± 0.1°C, vs RW, 0.2 ± 0.1°C; P = .001), but there were no significant differences in body temperature (WW, 0.1 ± 0.1°C, vs RW, 0.4 ± 0.1°C; P = .1). Net changes from diluent challenge for all parameters were compared between immersion of feet in WW and RW. Immersion of feet in WW significantly inhibited allergen-induced sneezes (WW, 5.7 ± 1.1, vs RW, 11.6 ± 3.2; P < .01), human serum albumin levels (WW, 941.7 ± 172.2 μg/mL vs RW, 1524.8 ± 220.6 μg/mL; P < .01), and secretion weights (WW, 30.5 ± 7.2 mg, vs RW, 41.8 ± 6.8 mg; P < .01). Conclusion: Our data show that warming of feet decreases the early response to nasal challenge with antigen. This inhibitory effect is probably related to the increase in the nasal mucosal temperature. (J Allergy Clin Immunol 1999;104:285-93.)