Effect of sodium cromoglycate on histamine inhalation tests

Sixteen adult asthmatic subjects in a clinical steady state were included in the study. On day 1, after baseline assessment of spirometry (FEV1, FEV1/FVC, FEF25-75), they underwent three to four consecutive inhalation tests using twofold increasing doses of histamine to measure the provocative concentration causing a fall in FEV1 of 20% (PC20). Baseline FEV1 was back to +/- 5% of the initial assessment before each histamine inhalation test (HIT). On days 2, 3, and 4, after baseline spirometry which confirmed that FEV1 was within 10% of initial day 1 assessment, placebo-lactose (P) or 40 mg of sodium cromoglycate (SCG) were nebulized in a double-blind randomized 4.3.1. two-treatment crossover study design. Ten minutes later, spirometry was repeated and followed by an HIT. Baseline spirometry was not significantly different on each day or after P and SCG. There was no statistical difference between the geometric means of the three or four PC20's done on day 1, indicating that there is no tachyphylaxis induced by repeated HIT. There was no statistical difference between mean PC20 after P (0.52 +/- 3.3 (SD) mg/ml), after SCG (0.50 +/- 3.2), and of the three to four HIT done on day 1 (0.40 +/- 3.6). We conclude that in asthmatic subjects SCG has no acute bronchodilator effect and does not alter the response to inhaled histamine.     

Changes in bronchial hyperreactivity induced by 4 weeks of treatment with antiasthmatic drugs in patients with allergic asthma: a comparison between budesonide and terbutaline

We performed a double-blind crossover study to compare the effects of long-term treatment of inhaled budesonide and terbutaline on bronchial hyperreactivity in 17 patients with allergic asthma. Both drugs were administered for 4 weeks with a placebo-treatment period before and after each active-treatment period. To assess bronchial hyperreactivity, standardized inhalation provocation tests with histamine and propranolol were performed every 2 weeks. Before each inhalation provocation the drugs were withheld for at least 12 hours. Before the budesonide treatment the FEV1 value (percent predicted) was 85.3 +/- 4.1% (mean +/- SEM). After 2 and 4 weeks of treatment with this drug, the value increased significantly to 89.4 +/- 4.1% and 96.2 +/- 3.8%, respectively (p less than 0.05 and p less than 0.005). The histamine provocation concentrations causing a decrease in FEV1 of 20% (PC20) on the same days were 4.0, 7.2, and 9.5 mg/ml, respectively (both p less than 0.001). The PC20 values for propranolol, which were measured 1 hour after the histamine provocation, were 11.7, 13.3, and 14.0 mg/ml (ns). The FEV1 values before and after 2 and 4 weeks of treatment with terbutaline were 86.2 +/- 4.0%, 84.8 +/- 4.1%, and 87.0 +/- 4.6%, respectively. The histamine PC20 values on the same days were 4.7, 3.1 (p less than 0.05), and 3.8 mg/ml, respectively. The propranolol PC20 values were 14.2, 8.7, and 10.1 mg/ml (p less than 0.001 and p less than 0.05, respectively. We conclude that budesonide improves bronchial hyperreactivity, possibly by a dampening of late allergic reactions, whereas treatment with terbutaline may lead to a temporary increase of bronchial hyperreactivity, possibly as a result of beta-receptor desensitization.     

Influence of a single antigenic challenge on the pattern of airway response to exercise in asthma.

We studied 14 atopic subjects with mild asthma (six men and eight females) to document whether allergen exposure can change the pattern of response to exercise. Each had an exercise test at 80% of the VO2 max for six minutes before (exercise 1) and 48 hours (exercise 2) after an allergen inhalation test (AIT). FEV1 was measured at regular intervals up to eight hours after each challenge. On the day following AIT, spontaneous changes in FEV1 were measured for eight hours (control day). Airway responsiveness (AR) to histamine was measured at the beginning of the study, then 24 hours after AIT and at the end of the 2nd exercise. Mean early fall in FEV1 after exercise 1, AIT and exercise 2 were, 24.9 +/- 3.2%, 24.5 +/- 2.2%, and 27.6 +/- 3.8%, respectively. Airway responsiveness to histamine was increased at 32 and 56 hours post-AIT with a mean PC20 (SEM) of 0.50 (0.40, 0.62) and 0.93 (0.74, 1.17) mg/mL compared with 1.87 (1.33, 2.61) at baseline (P less than .05). Allergen inhalation test induced an isolated early asthmatic response (EAR) in four subjects, an equivocal response (late fall in FEV1: 5% to 15%) in four and a definite late asthmatic response (LAR) in six. No subject had a LAR before the AIT but two with a LAR after allergen exposure developed a late response to exercise after the AIT. This last was only partly explained by an increased diurnal variation of expiratory flows.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of inhaled gallopamil, a potent calcium channel blocker, on the late-phase response in subjects with allergic asthma.

The effect of gallopamil on the late-phase response to inhaled allergen was evaluated in six young adults with allergic asthma in a crossover manner. During 2 study days, subjects received 20 mg of inhaled gallopamil or placebo 30 minutes before challenge with the same dose of allergen. In addition, a histamine challenge was performed 1 1/2 hours before and 24 hours after allergen challenge. On 2 additional study days, in the absence of allergen, basal airway responsiveness to histamine was measured before and after gallopamil or placebo administration. During the early phase, the mean +/- SD decrease in FEV1 was 28.0% +/- 11.3% after placebo and 25.1% +/- 8.4% after gallopamil administration (p greater than 0.05; beta = 0.14). During the late phase, the maximum decrease in FEV1 was 26.9% +/- 11.9% after placebo and 25.3% +/- 10.3% after gallopamil administration (p greater than 0.05; beta = 0.21). Airway reactivity to histamine 24 hours after allergen challenge could not be measured in three subjects after gallopamil administration and in one subject after placebo administration because of persistent bronchospasm. In contrast, basal responsiveness to histamine in the absence of allergen was modestly decreased by gallopamil. Since gallopamil is one of the most potent calcium channel blockers when it is administered by the inhaled route, it is unlikely that this group of drugs will be clinically useful for allergic asthma.     

Effect of inhaled diphemanil methylsulfate, a parasympatholytic agent, on histamine induced bronchoconstriction in asymptomatic asthmatics

Parenterally administered diphemanil methylsulfate, a quarternary ammonium compound with both parasympatholytic and direct bronchial smooth muscle relaxing properties, has been found effective in the treatment of bronchial asthma. The present study was undertaken to test the effectiveness of inhaled diphemanil in preventing histamine induced bronchoconstriction in asymptomatic adult asthmatics. Twenty subjects, aged 19-40 years (average 25) were studied, each on three different days, observing an interval of at least 70 hours between testing. On day one, airway sensitivity to inhaled histamine was determined. On days two and three, histamine challenge was repeated 20 minutes after inhalation of either diphemanil (2 mg) or its vehicle in a double-blind crossover design. Airway sensitivity was assessed by determining cumulative log dose units of inhaled histamine required to provoke a 20% decline in FEV1 (log PD20 - FEV1). Diphemanil did not prevent histamine induced bronchoconstriction nor did it significantly affect log PD20 - FEV1 (p = 0.59). We conclude that a 2 mg dose of diphemanil, administered by oral inhalation 20 minutes before histamine challenge, is ineffective in protecting against induced bronchospasm in asymptomatic adult asthmatics.     

An open study of auranofin in the treatment of steroid-dependent asthma

To determine the efficacy of oral gold in asthma, 20 patients with steroid-dependent asthma received auranofin at a dose of 3 mg by mouth, twice daily, in a 24-week open clinical trial. Prospective evaluation of bronchial responsiveness to methacholine was determined before and 8 and 16 weeks after initiation of auranofin therapy. Serial spirometry (FEV1 and FVC), lung volumes, and diffusing capacities (single breath carbon monoxide diffusing capacity of the lungs) were measured before and at 10 and 20 weeks after treatment. All subjects were required to record concomitant medications, symptom scores, and morning and evening peak expiratory flow rates. In vitro immunologic studies performed before and after 8 and 20 weeks of auranofin therapy included leukocyte histamine release in response to antihuman IgE, lymphocyte blast transformation in response to concanavalin A and phytohemagglutinin, and leukocyte inhibitory factor activity in response to Candida albicans and tetanus toxoid antigens. In 18 patients evaluated, there were no significant differences between baseline and posttreatment spirometry, single breath carbon monoxide diffusing capacity of the lungs, and lung volumes. At week 16 of treatment, the steroid cumulative dose or the total prednisone dose administered from 7 days before through 10 days after each methacholine test day decreased from a mean of 293 +/- 125 mg at baseline to 192 +/- 115 mg. At week 16, nine of 18 patients (50%) exhibited decreased methacholine responsiveness as defined by a more than one-half log10 increase in the concentration of methacholine causing a 20% decrease in FEV1. A significant correlation (r = 0.60) was observed between the increase in the concentration of methacholine causing a 20% decrease in FEV1 and the decrease in steroid cumulative dose after 16 weeks of treatment. Leukocyte histamine release to anti-IgE exhibited significant reductions from baseline at week 20 to 10(-2) (p less than 0.002) and at 10(-3) (p less than 0.005) dilutions. At week 20, leukocyte inhibitory factor activity in response to Candida increased from baseline at the 0.1 mg per well (p = 0.025) and 1 mg per well (p = 0.05) concentrations; similarly, the responses to tetanus toxoid increased at the 1 mg per well (p less than 0.05) and 0.1 mg per well (p less than 0.01) concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)     

The changes in plasma histamine levels after a sulpyrin inhalation test in asthmatic patients

A sulpyrin inhalation test was given to 13 patients with aspirin-induced asthma (AIA) and 8 patients with non-aspirin-induced asthma (non-AIA) to observe the changes in plasma histamine levels before and after challenges. The respiratory function (FEV1.0) was measured before and after sulpyrin inhalation. A decrease of more than 20% the initial value (basal value) was defined as a positive response. Plasma histamine was determined by high-performance liquid chromatography (HPLC). In 11 patients with AIA, a positive response was observed (SIT positive), with a fall of FEV1.0 to 63.70 +/- 4.87% of the basal value. In 2 patients with AIA and 8 patients with non-AIA, no positive response was observed (SIT negative). In patients with SIT positive, plasma histamine levels increased significantly from 0.61 +/- 0.06 ng/ml before challenges to 1.34 +/- 0.22 ng/ml after challenges (p less than 0.01). No significant changes of plasma histamine occurred in the SIT negative patients. These results suggest that mast cells play some role in the mechanism of the development of aspirin-induced asthma.     

Lack of acute effects of ascorbic acid on spirometry and airway responsiveness to histamine in subjects with asthma

Sixteen adult subjects with asthma in a clinical steady state were studied. On day 1, after baseline spirometry, they underwent four histamine inhalation tests with functional recovery between each test. The provocative concentration causing a 20% fall in FEV1 (PC20) was obtained after each test. On days 2, 3, and 4, after baseline spirometry, active and placebo ascorbic acid (2 gm) was administered orally, double-blind, according to a 4.3.1 two-treatment crossover study design. One hour later, spirometry was performed, and PC20 was reassessed. We found no significant changes in FEV1 and FVC after ascorbic acid as compared with placebo administration. There was no difference between PC20 on days 2, 3, and 4 and by standardizing for the four PC20 results obtained on day 1. We conclude that ascorbic acid has no acute bronchodilator effect and does not alter bronchial responsiveness to histamine in subjects with asthma.     

Monitoring of peak expiratory flow rates in subjects with mild airway hyperexcitability

Twenty-seven subjects with mild symptoms of bronchial hyperexcitability (cough, dyspnea, wheezing) and low to moderate degree of airway response to histamine monitored their peak expiratory flow rates (PEFR) for a mean +/- SD of 14.4 +/- 4.0 days. This assessment was performed without the use of any medication in 15 subjects, and before and after inhalation of salbutamol in 12 others. 100% and 52% of individuals, respectively, showed baseline FEV1 and maximum mid-expiratory flow rates greater than 80% of predicted. The improvement in FEV1 after salbutamol was less than 20% in every subject and from 10 to 20% in 15%. The mean daily percentage changes in PEFR were greater than the ones observed in normal individuals in only 21% and 50% of the subjects on no medication and on salbutamol, respectively. Diurnal changes in PEFR were significantly negatively correlated with the response to histamine (r = -0.51; p less than 0.01) and baseline FEV1 (r = -0.49; p less than 0.02). We conclude that there are minor fluctuations of PEFR in subjects with mild symptoms and low degree of airway excitability.     

The effect of nedocromil sodium on the bronchoconstrictor effect of neurokinin A in subjects with asthma

We have previously demonstrated that the neuropeptide, neurokinin A (NKA) (substance K), causes bronchoconstriction in subjects with asthma. In a double-blind, crossover study we investigated the effect of nedocromil sodium on NKA-induced bronchoconstriction in subjects with asthma. Twelve patients with mild asthma (mean FEV1 percent predicted +/- SE, 87.3 +/- 3.4) inhaled on 2 separate days either nedocromil sodium, 4 mg, or placebo, as two puffs from a metered-dose aerosol, 30 minutes before challenge with NKA. NKA was inhaled at three concentrations (10(-7), 3.10(-7), and 10(-6) mol/ml). The specific airway conductance (SGaw) and FEV1 were measured before and 5 and 15 minutes after each concentration step. On the placebo-treatment day, NKA caused a concentration-dependent decrease in SGaw and FEV1 (mean log for the provocative concentration of NKA causing a 35% fall in SGaw [10(-7) mol/ml], 0.49; mean log for the provocative concentration of NKA causing a 15% fall in SGaw [10(-7) mol/ml], 0.90). The inhalation of 4 mg of nedocromil sodium reduced the decrease in both SGaw and FEV1. The maximal percentage decrease in SGaw on the nedocromil sodium-treatment day was 27 +/- 5.2 (versus placebo, 53.3 +/- 5.4; p less than 0.05), and the maximal percentage decrease in FEV1 was 5.5 +/- 1.4 (versus placebo, 12.4 +/- 2.3; p less than 0.05). The dose-response curves for NKA after nedocromil sodium treatment were significantly shifted to the right compared to the curve after placebo-treatment. We conclude that nedocromil sodium protects against NKA-induced bronchoconstriction in subjects with asthma.     

The effect of inhaled allergen on circulating basophils in atopic asthma.

There is increasing evidence for the role of basophils in the allergen-induced late asthmatic response (LAR). To study the effect of inhaled allergen on basophil function in subjects with asthma, ex vivo basophil spontaneous histamine release (SHR) in peripheral blood and plasma histamine was measured before and 2, 5, 10, and 15 minutes, and 2, 4, 6, and 8 hours after allergen bronchial challenge (allergen study day) in six subjects with atopic asthma. Allergen inhalation induced an early response and LAR consisting of a mean (+/- SD) 32.5% (+/- 7.9%) and 28.8% (+/- 7.7%) fall in FEV1, respectively. As a control for the effects of bronchoconstriction, on another occasion, methacholine challenge was performed to produce a mean 33.4% (+/- 3.4%) fall in FEV1 during the early response and no LAR, and blood was obtained to measure basophil histamine release (HR) and plasma histamine. There was a small, but significant (p less than 0.05), rise in median SHR from 4.6% to 6.1% of total basophil histamine after allergen but not after methacholine inhalation. HR remained high after allergen inhalation during the 8 hours of study, whereas it demonstrated a steady, significant, decrease between 4 to 8 hours after methacholine inhalation. No significant changes in plasma histamine were recorded on either allergen or methacholine study days. On a third occasion, SHR was measured after challenge with physiologic saline to control for any effects of methacholine on SHR, and a decrease in HR was recorded during the day similar to HR observed after methacholine challenge. These studies suggest an enhancing effect of inhaled allergen on SHR.(ABSTRACT TRUNCATED AT 250 WORDS)     

Provocation with adenosine 5''-monophosphate, but not methacholine, induces sputum eosinophilia

INTRODUCTION: Bronchial hyper-responsiveness is usually measured with direct stimuli such as methacholine (MCh) or histamine. Adenosine 5'-monophosphate (AMP), which acts indirectly via the secondary release of mediators, is another stimulus to measure bronchial hyper-responsiveness. AIM: To investigate whether provocation with inhaled AMP itself initiates an inflammatory response resulting in an influx of eosinophils into the airway lumen. METHODS: We have included 21 non-smoking atopic asthmatic subjects (mean FEV1 101% predicted, mean age 34 years). Each subject performed three sputum inductions on different days, at least seven days apart: one without previous provocation, one hour after PC20 methacholine, and one hour after PC20 AMP. RESULTS: After provocation with AMP, but not methacholine, the percentage of sputum eosinophils increased significantly (from 1.9+/-0.5% to 4.5+/-1% (P<0.01) and 1.9+/-0.5% (P=0.89)). No changes in the percentages of neutrophils, lymphocytes, macrophages, or bronchial epithelial cells were found. CONCLUSION: A provocation test with AMP leads to an increased percentage of sputum eosinophils. This observation cannot be explained by a non-specific response of the airways to a vigorous bronchoconstriction, since methacholine had no effect on inflammatory cells.     

Hypomagnesemia and bronchial hyperreactivity

In a 37-year-old woman, a heavy smoker and an alcoholic, bronchial hyperreactivity to histamine (PC20 FEV1 0.8 mg/ml) was related to hypomagnesemia (0.55 mmol/l). After acute magnesium repletion (24 h i.v. infusion MgSO4 6 g, serum magnesium 1.05 mmol/l), histamine PC20 FEV1 increased up to 9.8 mg/ml. The role of magnesium in modulating smooth muscle contractility is discussed and the importance of checking serum magnesium in patients with airway obstruction is suggested.     

Inhibitory effects of azelastine hydrochloride in alcohol-induced asthma.

BACKGROUND: Alcohol-induced bronchoconstriction is due to high blood concentrations of acetaldehyde, a metabolic product of ethanol, which lead to the release of histamine from basophils and mast cells. OBJECTIVE: We examined the inhibitory effects of azelastine hydrochloride, which inhibits histamine release and blocks H1 receptors, in alcohol-induced asthma. METHODS: Subjects were 13 Japanese asthmatic patients. We measured the change in FEV1 after ingestion of 30 g of pure ethanol. Blood ethanol, acetaldehyde, histamine, leukotriene C4 (LTC4), and thromboxane B2 (TXB2) concentrations were also measured. Alcohol challenge test was repeated in responders after administration of azelastine for 1 week at 4 mg/day. RESULTS: Of 13 asthmatic patients, five (38.5%) tested positive during an ethanol challenge test, represented by a fall more than 20% in FEV1. The responders had a high blood ethanol, and showed a rise in blood acetaldehyde and histamine concentrations, but not in LTC4 or TXB2. After azelastine treatment, there was no significant fall in FEV1 among responders. Neither the rise in blood ethanol nor blood acetaldehyde levels were blunted by treatment with azelastine, but the rise in blood histamine was blunted by this treatment. CONCLUSION: Our results suggest that antihistamine agents may be effective against alcohol-induced asthma by both blocking H1 receptors and inhibiting histamine release.     

The in vivo potency and selectivity of azelastine as an H1 histamine-receptor antagonist in human airways and skin

Azelastine is a novel histamine H1 antagonist with putative antileukotriene activity in guinea pigs. With three different doses of oral azelastine, we have performed a dose-response study to determine its protective effect on the airways against histamine-induced bronchoconstriction in 12 patients with mild, atopic asthma. On 4 separate days, patients undertook standardized inhalation-challenge tests with increasing concentrations of histamine (0.03 to 32 mg/ml) 4 hours after placebo or azelastine, 4.4, 8.8, and 17.6 mg, administered double blind and in random order. On 2 additional days, patients underwent methacholine challenge tests after placebo or azelastine, 17.6 mg. Baseline FEV1 between treatment days and 4 hours after placebo and azelastine did not change significantly. The three doses of azelastine, 4.4, 8.8, and 17.6 mg, increased the concentration of histamine required to cause a 20% fall in FEV1 (PC20) from 0.16 mg/ml geometric mean (GM) after placebo to 1.98 (p less than 0.01), 8.8 (p less than 0.01), and 8.1 (p less than 0.01) mg/ml, respectively. GM potency ratios derived from the PC20 values obtained for each patient indicated that the three increasing doses of azelastine displaced the histamine dose-response curve to the right by factors of 12.8, 54.4, and 50.2. Azelastine had no effect on the airway response to methacholine with GM PC20 values of 0.16 and 0.19 after placebo and azelastine, 17.6 mg. Azelastine is a potent H1 histamine-receptor antagonist on human airways in vivo without demonstrable anticholinergic effect.     

Theophylline partially inhibits bronchoconstriction caused by inhaled histamine in subjects with asthma

Sixteen adult subjects in a clinical steady state had four consecutive histamine inhalation tests on the same day when they were not receiving oral theophylline medication. The provocative concentration of histamine causing a 20% fall in FEV1 (PC20) was used to assess the response. They were then administered active or placebo sustained-release theophylline preparations according to a double-blind, randomized 4.4.1. two-treatment crossover design. Medication was administered for a minimum of 3 consecutive days, and PC20 was reassessed on 4 different days, 3 to 4 hours after receiving active or placebo medication (two visits for each medication). A significant but small bronchodilator and blocking effect on histamine excitability was demonstrated for the active medication. This latter effect was present even by adjusting for changes in baseline airway caliber and for the intraindividual variability of the four PC20 values obtained on day 1. We conclude that theophylline partially blocks bronchial responsiveness to inhaled histamine.     

The effect of sputum induction on spirometry parameters in patients with bronchial asthma

Evaluation of differential cell count and biochemical parameters in sputum seems to be a valuable method in asthma studies. The purpose of the paper was to evaluate the effects of sputum induction alone and after fenoterol and salmeterol premedication, on spirometry in asthma patients. The another aim of the study was to observe the correlation between bronchial hyperreactivity and decreases in FEV1 and MEF50 in asthmatics during sputum induction. The studies were carried out on 20 mild to moderate asthma patients (FEV1 baseline 79 +/- 16% of the predicted values) who inhaled an increasing concentration of hypertonic saline (3%, 4% and 5%), using an ultrasonic nebuliser. The forced expiratory volume in one second and MEF50, as the good indicators of bronchial obturation, were evaluated. During the sputum induction significant decreases in FEV1 and MEF50 were observed, which were proportional to the concentration of NaCl. After inhalation of 3% of NaCl the mean of FEV1 was 87.2 +/- 12.7% of the baseline, after 4%--84.3 +/- 16.9% and 5%--77.4 +/- 19.8%. No significant correlation between bronchial hyperreactivity and the induced decreases in FEV1 and MEF50 were found. Fenoterol and salmeterol fully prevented bronchial obturation during sputum induction.     

Comparison of the intensity and duration of effects of inhaled bitolterol and albuterol on airway caliber and airway responsiveness to histamine

Inhaled beta-agonists can produce bronchodilatation and reduce airway hyperreactivity in patients with asthma. Using these two measures, we compared inhaled bitolterol (three puffs, 1110 micrograms), albuterol (two puffs, 180 micrograms), and placebo administered by metered-dose inhaler in a blinded, crossover study of 40 subjects with chronic asthma. On each study day, subjects underwent histamine challenges at 1 1/2 hours before, and 1/2, 2, 4, 6, and 8 hours after inhaling one of the three test-drug treatments. Both drugs produced significant bronchodilatation at 30 minutes through 4 hours and significant effects on airway reactivity at 30 minutes through 2 hours (p less than 0.05). Bitolterol also produced small but significant bronchodilator effects at 6 hours and effects on airway reactivity at 4 hours (p less than 0.05). Effects of bitolterol on airway reactivity diminished significantly more slowly than effects of albuterol in subjects with baseline provocative concentration causing a 20% fall in FEV1 greater than or equal to 1.0 mg/ml of histamine (half-life of biologic effect 1.37 versus 0.92 hours; p less than 0.05) but not in subjects with baseline provocative concentration causing a 20% fall in FEV1 less than or equal to 1.0 mg/ml (half-life of biologic effect of 1.01 versus 1.00 hours; p greater than 0.05).     

Seasonal variability of exercise-induced asthma especially outdoors. Effect of birch pollen allergy

A study was made to determine whether natural allergenic exposure modulates exercise-induced asthma. Eighteen asthmatic men, ten non-allergic and eight allergic to birch pollen, underwent heart rate-monitored outdoor exercise tests during both the cold winter season and in the spring, the birch pollen season. The mean fall in FEV1 after the outdoor exercise test increased in the allergic group from 17 +/- 3% in the winter to 27 +/- 6% in the spring, while it decreased in the non-allergic group from 31 +/- 6% to 22 +/- 4%, respectively (P less than 0.01). Initial FEV1 and FCV values remained unchanged in both groups. The non-specific airway responsiveness to histamine did not change significantly in birch pollen allergic or non-allergic subjects during the spring, when compared with the winter values. We conclude that the exercise-induced asthma is aggravated in the birch pollen allergic asthmatics during the pollen season, when compared to the non-birch pollen allergic asthmatics, in whom the exercise-induced bronchoconstriction is attenuated as expected, because of the warmer and more humid weather in the spring.