Hot, humid air partially inhibits the nasal response to allergen provocation.

Background: We have previously reported that preconditioning allergic subjects with hot, humid air (HHA) (temperature, 37 degrees C; relative humidity >95%) in an environmental chamber resulted in partial inhibition of the early response to nasal allergen challenge.
Objective: To investigate whether this inhibitory effect could be achieved by inhalation of HHA via a face mask.
Design: Randomized, 4-way crossover study.
Subjects: Eighteen subjects with seasonal allergic rhinitis participated in the study outside of their allergy season.
Interventions: Subjects underwent preconditioning with room air (RA) (temperature, 25 degrees C; relative humidity <20%) or HHA either in a chamber or delivered via a face mask for 1 hour prior to and during nasal challenge with diluent for the allergen extract followed by 2 increasing doses of allergen.
Results: Net changes from diluent challenge for all parameters were compared between HHA and RA in each delivery method. Hot, humid air delivered by mask significantly inhibited the mean+/-SEM number of allergen-induced sneezes (HHA, 2.7+/-0.6; RA, 6.6+/-2.1; P=.03), congestion score (HHA, 2.3+/-0.5; RA, 3.4+/-0.5; P=.01), and secretion weights (HHA, 26.9+/-4.4 mg; RA, 38.6+/-5.0 mg; P=.048). However, HHA inhaled in a chamber significantly inhibited only the mean+/-SEM allergen-induced congestion (HHA, 1.2+/-0.4; RA, 3.6+/-0.6; P=.002) and pruritus (HHA, 0.7+/-0.3; RA, 2.3+/-0.5; P=.002) scores.
Conclusions: Preconditioning the nasal mucosa with HHA partially decreases the early response to nasal challenge with antigen irrespective of the administration technique. The secretory response, however, is only inhibited by localized delivery of HHA to the nose. The inhibitory effects of HHA are therefore probably related to local changes in the nasal mucosa and are not dependent on total body exposure to HHA.