Study designs of evaluations included in the review
No restriction stated. Designs included: clinical trials, cross-sectional, prospective and longitudinal studies, which were double-, single- or un-blinded, randomised or non-randomised, controlled or uncontrolled.
Specific interventions included in the review
The use of vitamin C in asthma and allergy.
Participants included in the review
No restrictions stated. The studies included had differing populations: adults and children with asthma, healthy adults, adults with seasonal allergic rhinitis and sailors, plus two animal studies were included. No detailed characteristics of the patients are given.
Outcomes assessed in the review
Scurvy, incidence of asthma, plasma ascorbic acid levels, skin sensitivity, exercise-induced bronchospasm, severity and frequency of asthma attacks, methacholine challenge, airway tone, bronchoconstriction, cellular immunity, leukocyte function, histamine bronchoprovocation and pulmonary function.
How were decisions on the relevance of primary studies made?
The authors do not state how the papers were selected for the review, or how many of the authors performed the selection.