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The hygiene theory: fact or fiction?
Purpose of reviewThe "hygiene hypothesis" offers a potentially credible and parsimonious explanation for the increasing prevalence of allergy noted in many westernized populations. The authors review recent evidence both for and against this hypothesis.Recent findingsA strong body of epidemiologic evidence indicates that the original observations, namely of a birth order effect and increased risk of atopic disorders in those born into small, affluent households, are robust findings. Improved hygiene is believed to mediate its effect through decreased exposure to infectious agents in early life, and recent evidence has focused attention on the importance of the gastrointestinal microbial environment. In particular, infection with hepatitis A, Helicobacter pylori, and toxoplasma in those living in temperate climates, and geoheminths in those living in endemic areas, have been shown to be associated with reduced risk of atopic manifestations. It is postulated that these infections exert their effect through critically altering T-helper (Th)1/Th2 regulation, which is supported by the examination of the cytokine profiles of cord mononuclear cells when exposed to gastrointestinal flora and, furthermore, emerging evidence on the benefits of probiotics on symptoms of atopic dermatitis. Attempts to identify an inverse relation between Th1- and Th2-mediated disorders (as might be predicted by the Th1/Th2 paradigm) have, however, yielded conflicting results, raising the possibility that this model may be something of an oversimplification.SummaryThe hygiene hypothesis remains a credible but nonspecific explanation for observed variations over time, place and persons at risk for developing atopic allergic disorders. More prospective studies are needed to unravel which infectious agents exert a protective effect and the time period of importance for sensitization. The clinical implications of these advances in our understanding of the etiology of atopic allergic disorders are currently limited.
Topical treatments for seasonal allergic conjunctivitis: systematic review and meta-analysis of efficacy and effectiveness.
BackgroundEvidence for the effectiveness of topical treatments, in providing symptomatic relief from ocular allergy, remains uncertain.AimsTo assess the effectiveness and relative efficacy of topical treatments for the management of seasonal allergic conjunctivitis.Design of studyA systematic review and meta-analysis.SettingA literature search of the Cochrane Library, Medline, and EMBASE bibliographic databases.MethodDouble-masked randomised controlled trials were identified, that compared the use of topical mast cell stabilisers (sodium cromoglycate, nedocromil, lodoxamide) with placebo, topical antihistamines with placebo, and topical mast cell stabilisers with topical antihistamines.ResultsA meta-analysis of six trials showed that patients using sodium cromoglycate were 17 times (95% confidence interval [CI] = 4 to 78) more likely to perceive benefit compared with those using a placebo, although this estimate may be partially influenced by publication bias. Five trials indicated that those patients using nedocromil were 1.8 times (95% CI = 1.3 to 2.6) more likely to perceive their allergy to be moderately or totally controlled than those using a placebo. Four trials showed that those using antihistamines were 1.3 times (95% CI = 0.8 to 2.2) more likely to perceive a 'good' treatment effect than those using mast cell stabilisers, although this beneficial effect was not statistically significant. Limited evidence suggests that antihistamines might have a faster therapeutic effect compared to mast cell stabilisers.ConclusionOverall, these findings confirm the benefit of topical mast cell stabilisers and antihistamines over placebo for the treatment of allergic conjunctivitis. There is, however, insufficient evidence to recommend the use of one type of medication over another. Treatment preferences should therefore be based on convenience of use (with reduced frequency of instillation for some preparations), patient preference, and costs, especially as important side effects were not reported with any medication.
Burden of allergic disease in the UK: secondary analyses of national databases.
BackgroundAlthough allergy represents an important source of patient morbidity and healthcare utilization, there is little reliable information on the overall disease burden posed by allergic conditions in the UK.ObjectivesFocusing on the following conditions: allergic rhinitis, anaphylaxis, asthma, conjunctivitis, eczema/dermatitis, food allergy and urticaria/angioedema, we sought to (i) describe the prevalence, incidence and outcomes of allergic disorders; (ii) describe the NHS healthcare burden posed by allergic disorders; (iii) estimate the costs of allergic disorders from a healthcare perspective.MethodsSecondary analyses of data from the Health Survey for England, Scottish Health Survey, International Study of Allergies and Asthma in Childhood, European Community Respiratory Health Survey, Morbidity Statistics from General Practice 1991/1992, Royal College of General Practitioners Weekly Returns Service, Prescribing Analysis and Cost data, Hospital Episodes Statistics and national mortality data.ResultsThirty-nine percent of children and 30% of adults have been diagnosed with one or more atopic conditions. Six percent of general practice consultations and 0.8% of hospital admissions are for allergic diseases. Treatments for asthma and other allergic disorders currently account for 10% of primary care prescribing costs. Direct NHS costs for managing allergic problems are estimated at over one billion UK pounds per annum.ConclusionsAllergic disorders are common throughout the UK, affecting males and females of all ages and peoples from all social classes and ethnic groups. They currently represent a substantial burden of morbidity and health service cost.
Evaluation of an intervention to improve successful completion of the Mini-AQLQ: comparison of postal and supervised completion.
IntroductionPrevious postal administration of Mini Asthma-related Quality of Life Questionnaire (Mini-AQLQ) (validated for self-completion under supervision) resulted in 12.7% completion error rate.AimsTo administer the Mini-AQLQ by post with instructions, and to compare completion errors with our previous study and usable response rate with supervised self-completion.MethodThe Mini-AQLQ, with an instruction sheet, was posted to 96 participants from UK general practice, for completion 1 week before supervised self-completion in the surgery.Results94/96 (98%) postal questionnaires were returned: the error rate of 10.6% was similar to our previous study (postal versus previous: 10/94 versus 23/181: P=0.62). 86/96 (90%) attended for supervised completion with no completion errors (supervised versus postal: 0/86 versus 10/94: P=0.01) Overall usable response rates were similar. (supervised versus postal: 86/96 versus 84/96, P=0.65).ConclusionOur instruction sheet did not significantly reduce postal completion errors, however the good postal return rate achieved comparable overall usable response rates to supervised administration.