Hot, Humid Air for Allergies

ABSTRACT & COMMENTARY

Synopsis: An environment of 37°C, 90% humidity partially reduces the early response to allergen and may explain variable responses to allergen exposure on a given day.

Source: Desrosiers M, et al. Allergy Clin Immunol 1997; 99:77-86.

Various environmental factors have been thought to increase or decrease responsiveness to an allergen challenge. A nasal allergen challenge was performed on 10 subjects outside of their allergy season. They were pre-treated with either 20°C, 30% humidity (a control challenge) or 37°C, 90% humidity. There was a two-week separation between this crossover challenge. There was a significant protective effect of the pre-treatment with 37°C, 90% humidity as measured by significant decrease in histamine release, number of sneezes, pruritus, nasal airway resistance, congestion, and human serum albumin levels. The volume of secretions, runny nose, and lactoferrin levels were not affected. Thus, 37°C, 90% humidity partially reduces the early response to allergen and may explain variable responses to allergen exposure on a given day.

COMMENT BY SHELDON SPECTOR, MD

The non-pharmacologic treatment of various adverse stimuli in our environment, such as allergen- or rhinovirus-induced colds, is always welcomed. In fact, warm humidified air also has a protective effect on lower airway reactivity, as seen with exercise-induced asthma. Desrosiers et al were able to block an allergen challenge when given one hour prior to allergen exposure, delivered to the nose with pre-treatment of the air to 37°C and 90% relative humidity, so that core body temperature was also elevated. Both subjective and objective signs of amelioration were shown by reduction in total histamine release, sneezes, itchy nose, nasal airway resistance, and nasal congestion. There was no effect on the volume of secretions or runny nose.

The authors did not look at late allergen response in the nose, which would have been of added interest if it were included in the study design.1 Other investigators, such as Oppenheimer et al, found no effect on symptomatology or nasal patency in their population of patients with perennial rhinitis.2 They also found no protective effect on nasal challenge with allergen. However, whole body exposure was not employed. Additionally, their placebo device delivered supersaturated water droplets, which may not have been an ideal control. Other authors have confirmed the beneficial effect of elevated temperatures and humidity in patients with perennial allergies using slightly different designs.3-5 Although at present we do not understand the mechanism, a long, hot shower may become the non-pharmacologic treatment of choice to help protect someone from an allergic or viral trigger.

References

1. Spector SL (ed). Provocation Testing in Clinical Practice. New York: Marcel Dekker, Inc.; 1995.

2. Oppenheimer J, et al. J Allergy Clin Immunol 1993; 92:56-60.

3. Ophir D, et al. Ann Allergy 1988;60:239-242.

4. Yerushalmi A, et al. Proc Natl Acad Sci USA 1982;79: 4766-4770.

5. Johnston SL, et al. J Allergy Clin Immunol 1993;92: 850-856.