Effect Of Allergen Avoidance Research Articles

Antioxidant supplementation and exhaled nitric oxide in children with asthma.

The effect of allergen avoidance on airway inflammation is similar to that observed with treatment with inhaled steroids, whereas inhaled steroids have no effect on oxidative stress-induced inflammation. The aim of this study was to retrospectively evaluate the potential effect of an antioxidant dietary supplement on exhaled nitric oxide over a month in pediatric patients on stable antiasthma treatment. Forty-seven children with moderate-to-severe asthma were retrospectively evaluated. All the patients were sensitive to Dermatophagoides pteronyssinus and Dermatophagoides farinae, and they were receiving the minimum inhaled corticosteroid dosage required to maintain adequate control. Within a few weeks of admission at Misurina Hospital in the Alps, the regular treatment was gradually reduced, then some children who were receiving a daily dose of inhaled corticosteroids, ≤200 mcg of fluticasone propionate, were prescribed a nutraceutical dietary supplement for at least 4 weeks. Lung function and fractional exhaled nitric oxide (FeNO) measurements were recorded at the beginning and after 1 month of the dietary supplementation. Baseline lung function and FeNO values did not differ between the two groups of patients. After 4 weeks of nutraceutical supplementation, FeNO values decreased, from 19.00 ppb (interquartile range, 14-31 ppb) to 11.00 ppb (interquartile range, 6-23 ppb) (p = 0.03). No significant reduction was observed in the group that did not receive the supplementation, and no significant difference between groups was observed, both at baseline and after 4 weeks of nutraceutical supplementation. Supplementation with a nutraceutical of antioxidants and anti-inflammatory compounds, such as curcumin, resveratrol, soy phospholipids, zinc, selenium, and vitamin D, may be associated with reduced airway inflammation, as documented by a fall in FeNO.

Asthmatherapie im Hochgebirgsklima

Sojourns in the high mountains have been recommended to patients with asthma for many decades. It is the aim of this contribution to summarise the published studies about the effects of a stay at > 1500 m above sea level on asthmatic patients. These data from 428 adolescent and adult patients indicate an improvement of asthma symptoms and lung function during sojourns at high altitude. In many patients a reduction of the steroid therapy was achievable. Profound changes in the immune system have been demonstrated at high altitude, with a reduction of B- and T-helper cell activation. Total and mite-specific immunoglobulin E antibodies decrease significantly during longer sojourns. These changes are associated with a reduction of airway inflammation (e. g., reduction of eosinophil activation, NO exhalation and bronchial hyper-responsiveness). The fact that also patients with non-allergic asthma demonstrate a reduction of their airway inflammation at high altitude suggests that the high altitude climate has beneficial effects on asthma beyond the effects of allergen avoidance. High UV exposure and low humidity could be important additional factors, to explain the reductions in asthma severity in the high mountain climate. Larger controlled studies should be performed to prove the positive effects of the high altitude climate on asthma.

Possible Reasons for Lack of Effect of Allergen Avoidance in Atopy-Prone Infants and Sensitive Asthmatic Patients

The basic paradigm that allergen exposure produces atopic sensitization, and that continued exposure leads to clinical asthma throughout the development of airway inflammation and bronchial hyperreactivity has been challenged. However, because it was observed that epidemiological evidence suggests that around 40% of asthma cases are attributable to atopy (even using restrictive criteria), the obvious corollary is that if allergen avoidance begins before the onset of sensitization (primary prevention), then it should be associated with a reduced number of new cases of the disease. However, there are conflicting results regarding the effect of allergen avoidance on primary prevention of atopic sensitization and asthma onset. Instead, more uniform and positive results are available from secondary prevention studies. Secondary prevention obviously is an attractive opportunity for pediatricians who may recognize the patients who might benefit from these interventions simply by screening for food allergy in young children with atopic dermatitis. The conflicting results of tertiary prevention are most frequently observed in adult patients and sometimes result from incomplete avoidance of allergens responsible for the sensitization.

Allergen avoidance and prevention of atopy.

Recent increases in the prevalence of atopic disease argue strongly that environmental factors operating primarily in early life play a significant role. Exposure to food and inhalant allergens early in life may constitute a risk factor amenable to manipulation. Recent observational and interventional studies have produced conflicting data regarding the effectiveness of allergen avoidance in primary and secondary prevention of atopic diseases. Exclusive breast feeding for 4-6 months may protect against the development of allergic diseases in early childhood and remains good advice. Convincing proof for the preventive effects of the delayed introduction of solid foods and hydrolyzed formula in formula-fed infants is lacking. There is some evidence to support a preventive effect of house dust mite allergen avoidance before sensitization occurs. The effect of exposure to animal allergen is uncertain, with some studies showing an increase in sensitization while others suggest a protective effect. Therefore, no evidence-based advice can be given at this stage regarding allergen avoidance measures to be adopted by families with infants at high risk of atopy, except perhaps to breast feed exclusively for at least 4 months. Data regarding the secondary prevention of allergic disease by allergen avoidance were more secure until the publication this year of two randomized controlled trials which suggest that mattress impermeable covers, the main dust mite allergen avoidance measure, may not work. Allergen avoidance, however, should remain an essential part of the management of allergic diseases, even if the benefit of mattress covers is in doubt.

Effects of Allergen Avoidance at High Altitude on Children with Asthma or Atopic Dermatitis

Patients with atopic diseases benefit from a high-altitude climate, the effectiveness of which may be related to established house dust mite allergy. A relationship between these variables and disease severity as well as inflammatory activity has not been previously studied. The study objectives were: (1) to assess changes in inflammatory levels for children and adolescents with asthma or atopic dermatitis during a 4-week inpatient rehabilitation stay at high altitude, (2) to examine the role of house dust mite sensitization, and (3) to compare the results for the two diagnostic groups. A total of 115 children and adolescents aged 10-16 years were enrolled in the study: 60 suffered from asthma and 55 from atopic dermatitis. The prevalence of house dust mite sensitization was 36.52%. Urine and blood samples were collected on admission to an inpatient rehabilitation clinic and at their discharge 1 month later. Urinary eosinophil protein X (U-EPX) and serum eosinophil cationic protein (S-EPC)-levels were ana...

Predictors of lung function in infants at high risk of atopy: effect of allergen avoidance

Children of atopic parents are recognised as being at higher risk of developing bronchial asthma, drawing the attention of prevention strategies towards this population. Due to recent advances, lung function abnormalities in asthmatic children may now be measured early in life. The aim of this investigation was to examine possible predictors of lung function development in a sub sample of high-risk infants who took part in an allergy avoidance study. In 60 babies of atopic parents, measurements of upper airways inflammation were performed at 4 weeks of age, respiratory symptoms were assessed at 6 and 12 months of age, and lung function (Vmax,FRC) was measured at 18 months by the rapid thoracoabdominal compression technique. Twenty-eight babies were enrolled in an allergen avoidance program, and 32 recruited as controls. No significant differences were detected for V'max,FRC between the intervention group (mean 331 ml s−1) and the control group (359 ml s−1), P=0·382. A multiple linear regression model could explain levels of V'max,FRC by weight gain since birth (beta=−35·35 ml s−1 kg−1, P=0·022) and by eosinophilic cationic protein (ECP) (beta=−0·95 ml s−1 μ l−1, P=0·044), but not by intervention. Lung function measured at the age of 18 months in high-risk children is associated with weight gain and nasal ECP.

Therapy of allergic asthma

Asthma and atopy are strongly related conditions. The presence of specific IgE to perennial (arthropods, animal dander and other), seasonal (pollens, certain fungal spores) and occupational allergens is associated with the occurrence of asthmatic symptoms. Current therapy is based on combining three principles: Avoidance of trigger factors and of allergen exposure, drug therapy, and specific immunotherapy. Feasability and effectiveness of allergen avoidance (particularly of perennial allergens) have been proven. However, these measures must often be supplemented with drug therapy. Several classes of drugs are nowadays available for treatment of asthmatic symptoms and, most importantly, for control of the bronchial inflammatory process which underlies atopic asthma. Specific immunotherapy is a good treatment option in allergy to pollens, but its use is controversial in allergy to house dust mites and other perennial allergens. Finally, it should be kept in mind that the successful longterm management of patients with atopic asthma depends highly on the compliance of patients.

Indirect bronchial hyperresponsiveness in asthma: mechanisms, pharmacology and implications for clinical research.

Bronchial hyperresponsiveness (BHR), an abnormal increase in airflow limitation following the exposure to a stimulus, is an important pathophysiological characteristic of bronchial asthma. Because of heterogeneity of the airway response to different stimuli, the latter have been divided into direct and indirect stimuli. Direct stimuli cause airflow limitation by a direct action on the effector cells involved in the airflow limitation, while indirect stimuli exert their action essentially on inflammatory and neuronal cells that act as an intermediary between the stimulus and the effector cells. This manuscript reviews the clinical and experimental studies on the mechanisms involved in indirect BHR in patients with asthma. Pharmacological stimuli (adenosine, tachykinins, bradykinin, sodium metabisulphite/sulphur dioxide, and propranolol) as well as physical stimuli (exercise, nonisotonic aerosols, and isocapnic hyperventilation) are discussed. The results of the different direct and indirect bronchial challenge tests are only weakly correlated and are therefore not mutually interchangeable. Limited available data (studies on the effects of allergen avoidance and inhaled corticosteroids) suggest that indirectly acting bronchial stimuli (especially adenosine) might better reflect the degree of airway inflammation than directly acting stimuli. It remains to be established whether monitoring of indirect BHR as a surrogate marker of inflammation (in addition to symptoms and lung function) is of clinical relevance to the long-term management of asthmatic patients. This seems to be the case for the direct stimulus methacholine. More work needs to be performed to find out whether, indirect stimuli are more suitable in asthma monitoring than direct ones. Recommendations on the application of indirect challenges in clinical practice and research will shortly be available from the European Respiratory Society Task Force.

573 The effect of allergen avoidance in infancy on the development of respiratory symptoms and bronchial responsiveness

573 The effect of allergen avoidance in infancy on the development of respiratory symptoms and bronchial responsiveness

Clinical effects of allergen avoidance.

The costs of asthma care are increasing. A successful, simple and widely applicable environmental intervention could have major benefits. Although all trials of bed coverings suggest they are clinically effective, the impact of their widespread use by asthmatics has not been determined in a public health context. In 1992, the British Society of Allergy and Clinical Immunology Working Group reviewed all the published data and, agreed on the inadequancy of avoidance trials and the need for a large-scale study on mite-allergen avoidance (97). More recently, the Third International Workshop on Indoor Allergens and Asthma stated: “There is an urgent need to develop adequately-powered, randomised, controlled studies to investigate the potential benefits of low-allergen domestic environments in patients with allergic disease. Such studies need to address compliance, cost effectiveness, be of adequate length (e.g., 12 months), and be tailored for different socio-economic groups and age groups” (98). The 1997 revision of the British Thoracic Society Asthma Guidelines states: “Support for house dust mite avoidance measures reflects a change to the 1993 Guidelines, but further research into methodology and duration of action of these measures is needed” (99). There remains an urgent need to develop a large-scale trial of the widespread applicability of miteallergen avoidance and the effect on patient symptoms, exacerbation rate, use of medication, and overall health costs. One such study on the effect of mite-allergen avoidance by the use of allergen-impermeable bedding on asthma control in adults is currently being carried out in the United Kingdom (100). This is a randomized, parallel-group, double-blind, placebo-controlled trial, with 2000 patients entering the run-in period and 1800 being randomized. During the first 6 mo of the trial (phase A) patients will take their usual inhaled steroid therapy, and during the next 6 mo (Phase B, mo 6\2-12) patients will make a controlled reduction of inhaled steroids. The results of this study will show conclusively whether a simple intervention designed to reduce domestic mite-allergen exposure can improvethe clinical control of asthma, which subgroups of patients benefit, and whether a reduction in regular inhaled steroid use can be achieved in primary-care patients.

Atopy patch testing--a diagnostic tool?

Atopy patch testing--a diagnostic tool?

Differences in the effect of allergen avoidance on bronchial hyperresponsiveness as measured by methacholine, adenosine 5'-monophosphate, and exercise in asthmatic children.

Asthma is now considered as an inflammatory airway disease. There is evidence that allergen avoidance reduces clinical symptoms in atopic asthma. We investigated the effect of a month's stay in the hypoallergenic environment of Davos, Switzerland (1560 m) which is relatively free of house dust mite (HDM) on changes in bronchial hyperresponsiveness (BHR), using the challenge tests of adenosine 5'-monophosphate (AMP), exercise and methacholine to test for BHR. Thirteen asthmatic children with an allergy to HDM participated in the study. We measured BHR on admission to the Davos Asthma Center and after 1 month in the house dust-free environment. The medications used by the patients at the time of admission were kept unchanged during this month. No significant difference in BHR was found to methacholine challenge after a 1-month stay at high altitude (P > 0.05). By contrast, the response to AMP was significantly different as indicated by displacement of the dose-response curve to the right by 2.15 doubling concentrations (P = 0.005). We also observed a significant difference in response to exercise (P = 0.03). These results indicate that a month's stay in a hypoallergenic environment caused a reduction in BHR to AMP and exercise, but not to methacholine. In addition, the results support the concept of differences in trigger mechanisms for BHR, and that responses to a methacholine challenge are not the same as responses to an exercise challenge. The observed reduction in BHR in asthmatic children to the indirect bronchial stimuli of AMP and exercise suggest reduced airway inflammation following avoidance of house dust aeroallergens. AMP and exercise challenges may therefore be better indicators of asthmatic airway inflammation than the direct stimulus of methacholine.

Effect of allergen avoidance at high altitude on direct and indirect bronchial hyperresponsiveness and markers of inflammation in children with allergic asthma.

Improvement of allergic asthma is seen at high altitude partly because of low concentrations of allergen, especially house dust mite. To investigate the effect of a hypoallergenic environment (Davos, 1560 m) on airways inflammation, the changes in bronchial hyperresponsiveness measured with methacholine and adenosine 5'-monophosphate (AMP), blood eosinophils, eosinophil cationic protein (ECP), and serum IgE were studied. In 16 allergic asthmatic children tests were performed on admission and after one month. Medication was kept unchanged during the month of investigation and the patients performed peak expiratory flow (PEF) measurements twice daily. After one month at high altitude a considerable improvement was seen in the provocative concentration of AMP causing a 20% fall in forced expiratory volume in one second (PC20 AMP), but not with methacholine. There was also a reduction in total blood eosinophils and ECP. No change in serum IgE was observed. Peak flow variability decreased. After one month at high altitude a reduction in airways inflammation occurs. The results indicate that AMP responsiveness is a more accurate marker of disease activity in relation to inflammation in asthma than methacholine. The benefits of allergen avoidance at high altitude have important clinical implications for children with allergic asthma.

Effect of allergen avoidance in infancy on allergic manifestations at age two years

Background: One hundred twenty children, identified before birth as being at high risk for atopy, were prenatally assigned to prophylactic or control groups. Methods: The infants in the prophylactic group either received breast milk from mohters on an exclusion diet or an extensively hydrolyzed formula. Their bedrooms and living rooms were treated repeatedly with an acaricide, and they used polyvinyl-covered mattresses with vented head areas. The infants in the control group were fed conventionally, and no environmental control was recommended. Results: A significant advantage, first demonstrated at 1 year of age, persists for children in the prophylactic group. They have less of any allergy or eczema, but the reduced prevalence of asthma is no longer significant. Only three children in the prophylactic group had positive skin prick test results compared with 16 in the control group, suggesting a significant reduction in sensitization. Conclusion: A dual approach to allergen avoidance, focusing on foods and aeroallergens, appears to be beneficial in selected high-risk infants. Avoidance of potent allergens in early life increases the threshold for sensitization in these high-risk infants. Whether sensitization has been avoided or merely deferred has yet to be proved.