A systematic review including 40 studies was abstracted in DARE. Topical mast cell stabilisers (chromoglycate, nedocromil, lodoxamide) increased the proportion of patients perceiving benefit compared with placebo (12 trials, OR 4.9, 95% CI: 2.5 to 9.6). Sodium chromoglycate increased the proportion of patients perceiving benefit compared with placebo (6 trials, OR 17.2, 95% CI: 3.8 to 78.4). Nedocromil increased the proportion of patients reporting the allergy as moderately or totally controlled compared with placebo (OR 1.8, 95% CI: 1.3 to 2.6). The majority of studies on topical antihistamines (9 RCTs on levocabastine, azelastine or emedastine) did not report adequate data to allow an assessment of the benefit from treatment. Most of the studies found that antihistamines improved symptoms after provocation tests and improved allergic conjunctivitis when compared with placebo. All 6 longer term RCTs (duration: 14 days to 4 months) comparing mast-cell stabilizers and topical antihistamines found no statistically significant difference in outcome scores between treatments.
Comment: The quality of evidence is downgraded by heterogeneity and strong evidence for publication bias, but upgraded by strong association.