Effect of allergen challenge on airway responsiveness to histamine and sodium metabisulphite in mild asthma

Airway responsiveness to mannitol 24 h after allergen challenge in atopic asthmatics

BACKGROUND

Airway responsiveness to indirect stimuli correlates positively with airway inflammation. In atopic asthmatics, allergen inhalation is associated with an influx of inflammatory cells and increased responsiveness to the direct-acting stimuli methacholine at 3 and 24 h after exposure. We have shown mannitol responsiveness decreases 3 h after allergen inhalation. The current investigation assessed mannitol responsiveness 24 h after allergen challenge.

METHODS

Eleven mild atopic asthmatics completed allergen challenges on two separate occasions. In random order, methacholine or mannitol challenges were performed 24 h pre- and post-allergen challenge. Levels of fractional exhaled nitric oxide were also measured.

RESULTS

Allergen challenge increased airway responsiveness to methacholine 24 h postchallenge; the geometric mean (95% CI) methacholine PC20 decreased from 5.9 mg/ml (1.8-19.4) to 2.2 mg/ml (0.81-5.89); P = 0.01. This coincided with a significant increase (P = 0.02) in FeNO levels. Conversely, allergen challenge decreased airway responsiveness to mannitol; geometric mean (95% CI) dose-response ratio was significantly higher after allergen exposure (57 mg/% FEV1 fall [27-121] to 147 mg/% FEV1 fall [57-379]; P = 0.03), and FeNO levels were not significantly increased (P = 0.054).

CONCLUSION

Allergen-induced changes in airway responsiveness to direct and indirect stimuli are markedly different. The loss in responsiveness to mannitol is likely not explainable by a refractory state. The effect(s) of allergen exposure on airway responsiveness to indirect-acting stimuli require further investigation.

Cough, cough receptors, and asthma in children

This review discusses current general concepts on cough and the relationship between cough, cough receptor sensitivity, and asthma in children. It presents models of the relationship between cough and bronchoconstriction, and proposes a new model outlining the relationship between cough receptor sensitivity, airway hyperresponsiveness, and the clinical issues of cough, wheeze, and dyspnea in children with and without asthma. Cough is very common in children, with a prevalence of 15-20%. Those with non-specific cough (dry cough in the absence of identifiable respiratory illness) are often treated with a variety of drugs, in particular, medications for asthma and gastroesophageal reflux. However, there is little evidence to use these medications for the sole symptom of cough in children. Clinical studies on cough need to be interpreted in light of inherent methodological problems in studying cough. These methodological problems include the nonrepeatable nature of questions on cough, the unreliability of subjective measurements of cough, the lack of objective measurements to quantify cough severity, and the period effect (spontaneous resolution of cough). Although cough can be troublesome, cough serves as an important function for maintaining normal health of the respiratory system. The importance of cough in maintaining respiratory health is reflected in the development of lung atelactasis/collapse from retained secretions and recurrent pneumonia in clinical situations where the cough reflex is ineffective. The cough reflex is complex and still poorly understood. In this article the simplified cough pathway is presented and involves cough receptors, mediators of sensory nerves and the afferent pathway, the vagus nerve, the cough centre, efferent pathway, and cough effectors.

Wine-induced asthma: a placebo-controlled assessment of its pathogenesis

BACKGROUND

The sulfite family of food additives has been implicated in the pathogenesis of wine-induced asthma. However, the evidence supporting this is weak, and because wines have many hundreds of components, nonsulfite-associated mechanisms may also play a role.

OBJECTIVES

The aim of the study was to assess the potential sensitivity of persons with asthma to nonsulfite components in wine by using low-sulfite wine challenges.

METHODS

Sixteen adults with a strong history of wine-induced asthma were challenged with both low-sulfite red and white wines and wine-placebo drinks. Challenges were performed double blind, using a Latin square design, with lung function being assessed before the challenge and at 5, 10, 15, 30, and 60 minutes after the challenge. Subsequently, single-blind challenges with high-sulfite white wine were also completed in 10 individuals whose lack of reactivity to low-sulfite white wine suggested possible reactivity to sulfite additives.

RESULTS

The mean FEV1; forced expiratory flow, mid-expiratory phase; and peak expiratory flow of subjects to low-sulfite red and white wines and red and white placebo wines were not significantly different. Furthermore, with a predetermined criterion of a fall in FEV1 of more than 15% representing a positive challenge, only one individual exhibited a positive reaction in the presence of a negative response to placebo. Only 2 of the 10 test individuals who were challenged with a high-sulfite wine demonstrated a marked and rapid fall in FEV1. Reactivity to low-sulfite wines appears to occur only in a small number of individuals who report sensitivity to wines, suggesting that the sulfite additives may be the major cause of wine-induced asthmatic reactions. However, direct challenge with high-sulfite wine revealed only 2 clear reactions in this asthma cohort.

CONCLUSION

Wine-induced asthma appears to be a complex phenomenon and may involve several mechanisms that are codependent.