Dynamics of plasma levels of specific IgE in chlorhexidine allergic patients with and without accidental re-exposure.

BACKGROUND: Chlorhexidine is an effective disinfectant, which may cause severe allergic reactions. Plasma level of specific IgE to chlorhexidine (ImmunoCAP(®) ) has high estimated sensitivity and specificity when measured within 6 months of allergic reaction, but knowledge of the dynamics over longer time periods is lacking and it is unknown whether levels fall below <0.35 kUA/L in patients with previously elevated levels. It is also unclear whether re-exposure influences levels of specific IgE. OBJECTIVE: To investigate the dynamics of specific IgE in chlorhexidine allergic patients with and without re-exposure. METHODS: All patients diagnosed with chlorhexidine allergy in the Danish Anaesthesia Allergy Centre January 1999 to March 2015 were invited to participate. The study included blood samples from the time of reaction and time of investigation and blood samples drawn prospectively over several years. RESULTS: Overall, 23 patients were included. Specific IgE within hours of reaction was available in eight patients and was >0.35 kUA/L in six of these. During allergy investigations, usually 2-4 months later, specific IgE was >0.35 kUA/L in 22 of 23 patients. In the following months/years specific IgE declined <0.35 kUA/L in 17 of 23 patients (most rapidly within 4 months). Nine re-exposures in the healthcare setting were reported by seven patients (35%). Most re-exposures caused symptoms and were followed by an increase in specific IgE. Two patients with specific IgE <0.35 kUA/L reacted upon re-exposure. CONCLUSIONS & CLINICAL RELEVANCE: Time from reaction should be considered when interpreting specific IgE results. Specific IgE is >0.35 kUA/L in most patients at time of reaction but should be repeated after a few weeks/months if negative. The optimal sampling time seems to be >1 month and <4 months. A value <0.35 kUA/L neither excludes allergy nor implies loss of reactivity in previously sensitized patients. Re-exposures are common, often iatrogenic, and can cause a rebound in specific IgE.

Standardized testing with chlorhexidine in perioperative allergy--a large single-centre evaluation.

BACKGROUND: Perioperative allergic reactions to chlorhexidine are often severe and easily overlooked. Although rare, the prevalence remains unknown. Correct diagnosis is crucial, but no validated provocation model exists, and other diagnostic tests have never been evaluated. The aims were to estimate (i) the prevalence of chlorhexidine allergy in perioperative allergy and (ii) the specificity and sensitivity for diagnostic tests for chlorhexidine allergy. METHODS: We included all patients investigated for suspected perioperative allergic reactions in the Danish Anaesthesia Allergy Centre during 2004-2012. The following tests were performed: specific IgE (Immunocap® ; Phadia AB, Sweden), histamine release test (HR) (RefLab ApS, Denmark), skin prick test (SPT) and intradermal test (IDT). Positivity criteria were as follows: specific IgE >0.35 kUA/l; HR class 1-12; SPT mean wheal diameter ≥3 mm; IDT mean wheal diameter ≥ twice the diameter of negative control. Chlorhexidine allergy was post hoc defined as a relevant clinical reaction to chlorhexidine combined with two or more positive tests. Based on this definition, sensitivity and specificity were estimated for each test. RESULTS: In total, 22 of 228 patients (9.6%) met the definition of allergy to chlorhexidine. Estimated sensitivity and specificity were as follows: specific IgE (sensitivity 100% and specificity 97%), HR (sensitivity 55% and specificity 99%), SPT (sensitivity 95% and specificity 97%) and IDT (sensitivity 68% and specificity 100%). CONCLUSIONS: In patients investigated for suspected perioperative allergic reactions, 9.6% were diagnosed with allergy to chlorhexidine. Using our definition of chlorhexidine allergy, the highest combined estimated sensitivity and specificity was found for specific IgE and SPT.

Recommendations for the standardization of clinical outcomes used in allergen immunotherapy trials for allergic rhinoconjunctivitis: an EAACI Position Paper.

BACKGROUND: Allergen immunotherapy (AIT) has been thoroughly documented in randomized controlled trials (RCTs). It is the only immune-modifying and causal treatment available for patients suffering from IgE-mediated diseases such as allergic rhinoconjunctivitis, allergic asthma and insect sting allergy. However, there is a high degree of clinical and methodological heterogeneity among the endpoints in clinical studies on AIT, for both subcutaneous and sublingual immunotherapy (SCIT and SLIT). At present, there are no commonly accepted standards for defining the optimal outcome parameters to be used for both primary and secondary endpoints. METHODS: As elaborated by a Task Force (TF) of the European Academy of Allergy and Clinical Immunology (EAACI) Immunotherapy Interest Group, this Position Paper evaluates the currently used outcome parameters in different RCTs and also aims to provide recommendations for the optimal endpoints in future AIT trials for allergic rhinoconjunctivitis. RESULTS: Based on a thorough literature review, the TF members have outlined recommendations for nine domains of clinical outcome measures. As the primary outcome, the TF recommends a homogeneous combined symptom and medication score (CSMS) as a simple and standardized method that balances both symptoms and the need for antiallergic medication in an equally weighted manner. All outcomes, grouped into nine domains, are reviewed. CONCLUSION: A standardized and globally harmonized method for analysing the clinical efficacy of AIT products in RCTs is required. The EAACI TF highlights the CSMS as the primary endpoint for future RCTs in AIT for allergic rhinoconjunctivitis.

Post-treatment efficacy of discontinuous treatment with 300IR 5-grass pollen sublingual tablet in adults with grass pollen-induced allergic rhinoconjunctivitis.

BACKGROUND: Sustained efficacy over three pollen seasons of pre- and co-seasonal treatment with 300IR 5-grass pollen sublingual tablet has been demonstrated in adults with moderate-severe grass pollen-associated allergic rhinoconjunctivitis. OBJECTIVE: To assess the efficacy of discontinuous treatment with 300IR 5-grass pollen sublingual tablet during the post-treatment pollen season of this long-term study. METHODS: Adults aged 18-50, sensitized to grass pollen, with a history of allergic rhinoconjunctivitis for more than two pollen seasons, and a retrospective rhinoconjunctivitis total symptom score ≥ 12 (0-18 scale), were randomized to receive Placebo or a 300IR tablet daily beginning either 4 months (4M) or 2 months (2M) prior to each pollen season and continuing for its duration for three consecutive years. They were followed over the subsequent immunotherapy-free pollen season. Post-treatment efficacy was evaluated using the Average Adjusted Symptom Score (AAdSS, adjusting the Rhinoconjunctivitis Total Symptom Score for rescue medication usage) during the post-treatment pollen period. Secondary endpoints included Average Rhinoconjunctivitis Total Symptom Score (ARTSS), Average Rescue Medication Score (ARMS), overall Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) score and safety evaluation. Efficacy variables were analysed using ancova. RESULTS: Overall, 435 patients contributed to the Year 4 efficacy analyses. The Least-Squares (LS) mean differences (95% confidence interval) in AAdSS between active treatment and Placebo over the fourth pollen period were -1.14 (-2.03; -0.26) (P = 0.0114) and -1.43 (-2.32; -0.53) (P = 0.0019) in the (4M) and (2M) groups, corresponding to -22.9% and -28.5% relative LS mean differences (vs. Placebo) respectively. The active groups also showed statistically significant differences compared to Placebo in ARTSS, ARMS and overall RQLQ score. No safety risk was identified during the post-treatment period. CONCLUSIONS AND CLINICAL RELEVANCE: Pre- and co-seasonal treatment with 300IR 5-grass pollen sublingual tablet administered discontinuously for three consecutive years is efficacious post-treatment, safe and well tolerated. Benefits of treatment were meaningful to patients.

Analysis of allergen immunotherapy studies shows increased clinical efficacy in highly symptomatic patients.

BACKGROUND: The assessment of allergen immunotherapy (AIT) efficacy in the treatment for seasonal allergic rhinoconjunctivitis (SAR) symptoms is challenging. Allergen immunotherapy differs from symptomatic therapy in that while symptomatic therapy treats patients after symptoms appear and aims to reduce symptoms, AIT is administered before symptoms are present and aims to prevent them. Thus, clinical studies of AIT can neither establish baseline symptom levels nor limit the enrolment of patients to those with the most severe symptoms. Allergen immunotherapy treatment effects are therefore diluted by patients with low symptoms for a particular pollen season. The objective of this analysis was to assess the effect possible to achieve with AIT in the groups of patients presenting the most severe allergic symptoms. METHODS: Study centres were grouped into tertiles categorized according to symptom severity scores observed in the placebo patients in each centre (low, middle and high tertiles). The difference observed in the average score in each tertile in active vs placebo-treated patients was assessed. This allowed an estimation of the efficacy that could be achieved in patients from sites where symptoms were high during the pollen season. RESULTS: An increased treatment effect was observed in the most severe patients and was independent of the study analysed and symptom score used. CONCLUSIONS: The use of a tertile approach to analyse efficacy in AIT in SAR clinical studies can give a more accurate assessment of potential clinical benefit.

Sublingual allergen immunotherapy: mode of action and its relationship with the safety profile.

Allergen immunotherapy reorients inappropriate immune responses in allergic patients. Sublingual allergen immunotherapy (SLIT) has been approved, notably in the European Union, as an effective alternative to subcutaneous allergen immunotherapy (SCIT) for allergic rhinitis patients. Compared with SCIT, SLIT has a better safety profile. This is possibly because oral antigen-presenting cells (mostly Langerhans and myeloid dendritic cells) exhibit a tolerogenic phenotype, despite constant exposure to danger signals from food and microbes. This reduces the induction of pro-inflammatory immune responses leading to systemic allergic reactions. Oral tissues contain relatively few mast cells and eosinophils (mostly located in submucosal areas) and, in comparison with subcutaneous tissue, are less likely to give rise to anaphylactic reactions. SLIT-associated immune responses include the induction of circulating, allergen-specific Th1 and regulatory CD4+ T cells, leading to clinical tolerance. Although 40-75% of patients receiving SLIT experience mild, transient local reactions in the oral mucosa, these primary reactions rarely necessitate dose reduction or treatment interruption. We discuss 11 published case reports of anaphylaxis (all nonfatal) diagnosed according to the World Allergy Organization criteria and relate this figure to the approximately 1 billion SLIT doses administered worldwide since 2000. Anaphylaxis risk factors associated with SCIT and/or SLIT should be characterized further.

European Academy of Allergy and Clinical Immunology task force report on 'dose-response relationship in allergen-specific immunotherapy'.

BACKGROUND: For a century, allergen-specific immunotherapy (SIT) has proven to be an effective treatment for allergic rhinitis, asthma, and insect sting allergy. However, as allergen doses are frequently adapted to the individual patient, there are few data on dose-response relationship in SIT. Allergen products for SIT are being increasingly required to conform to regulatory requirements for human medicines, which include the need to demonstrate dose-dependent effects. METHODS: This report, produced by a Task Force of the EAACI Immunotherapy Interest Group, evaluates the currently available data on dose-response relationships in SIT and aims to provide recommendations for the design of future studies. RESULTS: Fifteen dose-ranging studies fulfilled the inclusion criteria and twelve reported a dose-response relationship for clinical efficacy. Several studies also reported a dose-response relationship for immunological and safety endpoints. Due to the use of different reference materials and methodologies for the determination of allergen content, variations in study design, and choice of endpoints, no comparisons could be made between studies and, as a consequence, no general dosing recommendations can be made. CONCLUSION: Despite recently introduced guidelines on the standardization of allergen preparations and study design, the Task Force identified a need for universally accepted standards for the measurement of allergen content in SIT preparations, dosing protocols, and selection of clinical endpoints to enable dose-response effects to be compared across studies.

How to design and evaluate randomized controlled trials in immunotherapy for allergic rhinitis: an ARIA-GA(2) LEN statement.

Specific immunotherapy (SIT) is one of the treatments for allergic rhinitis. However, for allergists, nonspecialists, regulators, payers, and patients, there remain gaps in understanding the evaluation of randomized controlled trials (RCTs). Although treating the same diseases, RCTs in SIT and pharmacotherapy should be considered separately for several reasons, as developed in this study. These include the severity and persistence of allergic rhinitis in the patients enrolled in the study, the problem of the placebo, allergen exposure (in particular pollen and mite), the analysis and reporting of the study, the level of symptoms of placebo-treated patients, the clinical relevance of the efficacy of SIT, the need for a validated combined symptom-medication score, the differences between children and adults and pharmacoeconomic analyses. This statement reviews issues raised by the interpretation of RCTs in sublingual immunotherapy. It is not possible to directly extrapolate the rules or parameters used in medication RCTs to SIT. It also provides some suggestions for the research that will be needed. Interestingly, some of the research questions can be approached with the available data obtained from large RCTs.

The T cell response to major grass allergens is regulated and includes IL-10 production in atopic but not in non-atopic subjects.

BACKGROUND: The incidence of allergic diseases is increasing in industrialized countries and the immunological mechanisms leading to tolerance or allergy are poorly understood. Cytokines with suppressive abilities and CD4(+)CD25(+) regulatory T cells have been suggested to play a central role in allergen-specific responses. The aim was to determine whether major grass allergens induce production of suppressive cytokines in allergic and healthy subjects and to examine the inhibitory effect of these cytokines on allergic responses. METHODS: Peripheral blood mononuclear cells (PBMCs) were isolated from healthy and grass-allergic donors and stimulated with the major grass allergens Phl p 1 or Phl p 5. The effects of endogenous IL-10 and/or TGF-beta on proliferation and cytokine production were determined by use of blocking antibodies. In addition, the number of CD4(+)CD25(+) T cells and their expression of chemokine receptors were investigated by flow cytometry. RESULTS: Phl p 1 and Phl p 5 induced IL-10 production, which down-regulated proliferation and cytokine production, in PBMC cultures from atopic but not from non-atopic donors. Comparable frequencies of CD4(+)CD25(+) T cells were present in PBMCs in the two groups, but fewer cells from atopic donors were CD4(+)CD25(+)CCR4(+) and more cells were CD4(+)CD25(+)CLA(+) compared to healthy donors. CONCLUSION: Allergen-specific responses of grass allergic patients but not in non-atopic subjects are influenced by regulatory cytokines produced in response to the important allergens. Differences in CD4(+)CD25(+) T cell expression of chemokine receptors in allergic compared to non-atopic donors could suggest that the homing of CD4(+)CD25(+) T cells is important for the regulation of allergen-specific responses.

Efficacy and safety of 5-grass pollen sublingual immunotherapy tablets in patients with different clinical profiles of allergic rhinoconjunctivitis.

BACKGROUND: The optimal dose of grass pollen tablets for sublingual immunotherapy (SLIT) in allergic rhinoconjunctivitis patients was previously established in a multinational, randomized, double-blind, placebo-controlled study in 628 adults. Patients were randomized to receive once-daily 5-grass pollen sublingual tablets of 100 IR (index of reactivity), 300 IR or 500 IR, or placebo starting 4 months before the pollen season. OBJECTIVE: The aim of this complementary analysis was to determine whether 300 IR 5-grass pollen SLIT-tablets is effective in different subtypes of patients who are allergic to grass pollen. METHODS: Different subgroups could be identified regarding comorbidities (with or without asthma during the grass-pollen season), sensitization (mono/polysensitization) and symptom severity. An additional exploratory analysis was performed within four subgroups based on pre-treatment assessment: Group 1=high specific IgE; Group 2=high symptom scores; Group 3=high skin sensitivity; Group 4=any of Group 1, 2 or 3. RESULTS: Asthma and sensitization status were not significant covariates as the average Rhinoconjunctivitis Total Symptom Score (RTSS) was identical for patients with and without grass-pollen asthma, as well as for mono- and polysensitized patients. Across the four subgroups, average RTSSs (+/- SD) for the optimal dosage (300 IR) were 3.91 +/- 3.16, 3.83 +/- 3.14, 2.55 +/- 2.13 and 3.61 +/- 2.97, for subgroups 1, 2, 3 and 4, respectively. ANCOVA showed that in Group 1 average RTSS did not differ significantly with different doses of SLIT. In Groups 2, 3 and 4, doses of 300 IR and 500 IR were significantly more effective than 100 IR and placebo (P< or =0.035). All doses of SLIT administered in this study can be considered safe in the patients investigated. CONCLUSIONS: The risk-benefit ratio validates the use of 300 IR tablets in clinical practice in all of these patient subgroups, regardless of severity profile, sensitization status and presence of asthma.

The CONSORT statement checklist in allergen-specific immunotherapy: a GA2LEN paper.

The methodology of randomized clinical trials is essential for the critical assessment and registration of therapeutic interventions. The CONSORT (Consolidated Standards of Reporting Trials) statement was developed to alleviate the problems arising from the inadequate reporting of randomized controlled trials. The present article reflects on the items that we believe should be included in the CONSORT checklist in the context of conducting and reporting trials in allergen-specific immunotherapy. Only randomized, blinded (in particular blinding of patients, health care providers, and outcome assessors), placebo-controlled Phase III studies in this article. Our analysis focuses on the definition of patients' inclusion and exclusion criteria, allergen standardization, primary, secondary and exploratory outcomes, reporting of adverse events and analysis.

Safety and immunological changes during sublingual immunotherapy with standardized quality grass allergen tablets.

Immunotherapy is the only treatment for allergy that has the potential to alter the natural course of the disease. Sublingual immunotherapy for grass pollen-induced rhinoconjunctivitis has been developed to make immunotherapy available to a broader group of allergic patients. Here, a safe dose range and the safety during daily sublingual administration were investigated for a new tablet-based sublingual immunotherapy for grass pollen allergy. Simultaneously, immunological changes were monitored. A randomized, double-blind, placebo-controlled phase I trial was undertaken, with stepwise dose-escalation during the dose-finding period, and afterwards with daily dosing 8 weeks prior to and 15 weeks during the grass pollen season (2500, 25000, or 75000 standardized quality tablet [SQ-T] units, or placebo). Fifty-two participants with grass pollen-induced rhinoconjunctivitis and a positive skin prick test and specific IgE to Phleum pratense entered the trial. During the daily-dose treatment periods, 67% of the participants reported adverse events. The most frequent were itching in the mouth, eyes, or throat, and rhinitis, and most were mild and resolved within 1 day. Two participants withdrew due to adverse events (sting and blisters in the mouth and itching in the mouth). Time- and dose-dependent increases of P pratense-specific IgG, IgA, IgE, and IgE-competing components were found in serum during the first 8 weeks of daily dosing, indicating that the treatment had a significant allergen-specific effect on the immune system. In conclusion, the grass allergen tablet, administered in a dose of 75000 SQ-T once daily, was well tolerated and displayed systemic immunogenicity.

Allergy immunotherapy across the life cycle to promote active and healthy ageing: from research to policies: An AIRWAYS Integrated Care Pathways (ICPs) programme item (Action Plan B3 of the European Innovation Partnership on active and healthy ageing) and the Global Alliance against Chronic Respiratory Diseases (GARD), a World Health Organization GARD research demonstration project.

Allergic diseases often occur early in life and persist throughout life. This life-course perspective should be considered in allergen immunotherapy. In particular it is essential to understand whether this al treatment may be used in old age adults. The current paper was developed by a working group of AIRWAYS integrated care pathways for airways diseases, the model of chronic respiratory diseases of the European Innovation Partnership on active and healthy ageing (DG CONNECT and DG Santé). It considered (1) the political background, (2) the rationale for allergen immunotherapy across the life cycle, (3) the unmet needs for the treatment, in particular in preschool children and old age adults, (4) the strategic framework and the practical approach to synergize current initiatives in allergen immunotherapy, its mechanisms and the concept of active and healthy ageing.

A sensitive and reproducible method for the determination of subnanogram quantities of immunoglobulin E (IgE).

An immunoradiometric assay for immunoglobulin E (IgE) using high adsorption polystyrene test tubes as the solid phase (the 'Maxisorp' assay) is described. The sensitivity of the method was found to be 50 pg IgE/ml and the within-assay reproducibility was 3-7%. The accuracy was estimated by means of a comparison between the Maxisorp assay and paper radioimmunosorbent test (PRIST) and a correlation coefficient of 0.98 (P less than 0.001) was obtained. We conclude that the Maxisorp assay is a fast and reliable assay for IgE determination in cord blood, cell culture supernatants and other highly diluted IgE preparations.

Allergen-specific immunotherapy in allergic rhinitis.

The scope of this review is to highlight important and interesting articles in the field of allergen-specific immunotherapy in allergic rhinitis published within the past year. The review is not intended to give a full overview of published literature but rather to focus on some subjects that I find significant in relation to the understanding of the specific treatment of allergies and to the selection of different treatment modalities. The most important aspects are how to define the most suitable candidates for the specific treatment, the mechanisms of action of immunotherapy and how to optimize treatment, and finally I include some reflections on the optimal presentation of the allergen to the immune system.

Minimising the risks of allergen-specific injection immunotherapy.

The clinical advantages of allergen-specific immunotherapy are counterbalanced by the risk of inducing systemic adverse effects. Although the frequency of life-threatening systemic reactions is low, the treatment carries a risk of inducing anaphylactic reactions. A fundamental point in risk assessment is to use a clinically meaningful and internationally accepted grading system for reactions. Of importance in minimising the risk of systemic adverse effects is the identification of at-risk patients and factors, the institution of procedures for monitoring patients before injections, and the adjustment of dosages in accordance with defined rules. Asthma, especially uncontrolled asthma, is a significant risk factor for the induction of systemic reactions. Likewise, dose escalation during allergen exposure, i.e. during pollen seasons, increases the risk of adverse effects. It is recommended that standardised extracts with a documented potency and consistency between production batches are used in order to prevent overdose when changing to a new vial. The intensity of the induction regimen is a balance between the risk of inducing systemic reactions and the time required to administer the regimen. Single injections once a week are generally well tolerated, in contrast to rush immunotherapy which may carry an increased frequency of adverse effects. A clustered induction regimen (2 to 4 injections per visit) represents a compromise of a patient-friendly fast regimen without an unacceptably high frequency of systemic reactions. A major issue in improving the safety of allergen injections is minimising the human factor, e.g. mistakes of patient identification, allergen extracts and dosages. Meticulous care in monitoring every patient before the injection, which requires education and training of the staff in the dosage decision process, is the cornerstone in reducing adverse effects. Involving the patient actively in the safety monitoring process might be helpful and improves patient compliance by allowing the patient to be an active partner in the treatment. Finally, if anaphylactic reactions are induced, a successful outcome is related to the staff being able to identify the early signs and to institute immediate rescue treatment. A quality assurance programme is the optimal way to minimise the risk of immunotherapy-associated systemic reactions.

[Allergen-specific immune therapy in the treatment of asthma]. / Allergenspecifik immunterapi ved behandling af asthma.

OBJECTIVES: 1. To identify all published randomised controlled trials of allergen specific immunotherapy in asthma. 2. To estimate the overall efficacy of allergen specific immunotherapy upon asthmatic symptoms, medication requirements, lung function, nonspecific bronchial hyperreactivity (BHR) and allergen specific BHR. SEARCH STRATEGY: A search of the asthma database by the Cochrane Airways Group at St. Georges Hospital Medical School, London identified 660 nonunique citations with the keywords Immunotherapy* or Hyposensitive or Desensiti*. This database included all studies published up to 1997 with the keywords Asthma or Wheez* from the Medline, Embase and Cinahl databases, together with other studies identified by handsearching. SELECTION CRITERIA: The review was restricted to randomised controlled trials (RCT). Only studies which focussed upon asthma were included. Allergen specific immunotherapy was defined as the subcutaneous administration of extracts of house dust mites, pollens, animal danders or moulds, chemically modified allergoids or antigen-antibody complexes. Although placebo controlled trials were methodologically stronger, studies which administered house dust or other relatively antigenically inactive preparations to the control group were also considered. Double blinded trials were preferred, but single blind and open studies were also reviewed for possible inclusion. At least one of the following clinical outcomes had to be reported: asthmatic symptoms, asthma medication requirements, lung function, nonspecific BHR or allergen specific BHR. Inclusion of studies in the review was decided by a simple majority of all three reviewers, who independently read the methods sections of papers identified by the search strategy and applied the stated criteria. Quality assessment was performed by 2 reviewers, who independently assessed the concealment of allocation. DATA COLLECTION AND ANALYSIS: The comparisons were: Allergen immunotherapy v placebo, Allergen immunotherapy v antigenically inactive control, House dust v placebo and Allergen immunotherapy v untreated control. These comparisons were performed separately for each outcome, whenever these results were reported. Outcome data were extracted and entered into RevMan 3.0.1 for statistical analysis. Categorical outcomes were analysed as odds ratios (OR) and 95% confidence intervals (95% CI) calculated by Peto's method. Continuous outcomes were analysed as standardised mean differences (SMD). Fixed effects models were used to obtain summary statistics for the overall efficacy of allergen immunotherapy and x2 tests were performed to assess heterogeneity between studies. MAIN RESULTS: Fifty four randomised controlled trials published between 1954 and 1997 satisfied the inclusion criteria. There were 25 studies reporting immunotherapy for mite allergy, 13 studies of pollen allergy, eight studies of animal dander allergy, two studies of allergy to the mould Cladosporium and six studies which attempted simultaneous immunotherapy for multiple aeroallergens. Concealment of allocation was assessed as clearly adequate in only 11 studies. The adequacy or otherwise of 40 studies could not be determined from the details published in the papers. Only three studies used a clearly inadequate method for concealment of allocation. There was a significant overall improvement in asthma symptom scores following immunotherapy (combined SMD -0.52; 95% -0.70 to -0.35). Patients randomised to immunotherapy were also significantly less likely to report a deterioration in asthma symptoms than those randomised to placebo (OR 0.27; 95% CI 0.21 to 0.35). Asthma medication requirements were significantly reduced (SMD -0.51; 95% CI -0.74 to -0.28). Patients randomized to immunotherapy were also significantly less likely to require medication than those randomised to placebo (OR 0.28; 95% CI 0.19 to 0.42). There was no overall improvement in lung function following immunotherapy and marked hete