The outcomes used are not clearly defined. No criteria to check the validity or relevance of included studies are given. Studies which are described in the results section are not included in the Tables of studies. The majority of studies reported are very small. The studies are not ordered by methodological strength and so it is difficult to untangle the level of evidence for the various findings.
Further research is needed before the use of vitamin C in asthma and allergy can be supported.
1998 Database no.