EVIDENCE-BASED ANSWER:
Topical antihistamines and topical mast cell stabilizers appear to reduce conjunctival injection and itching effectively. Topical nonsteroidal anti-inflammatory drugs (NSAIDs) are also effective, but may sting on application (strength of recommendation: B, meta-analysis of randomized controlled trials [RCTs]).
Both of these treatments relieve redness and itching
A 2004 systematic review of 40 RCTs (total N not provided) assessed the efficacy of topical treatment with mast cell stabilizers and antihistamines, comparing each with the other and placebo.1 Eleven trials that included 899 children and adults compared mast cell stabilizers (sodium cromoglycate, nedocromil, and lodoxamide tromethamine) with placebo. Follow-up periods ranged from 4 to 9 weeks.
Because of study heterogeneity, a random-effects model was used and showed that topical mast cell stabilizers relieved symptoms (ocular itching, burning, and lacrimation) 4.9 times more effectively than placebo (95% confidence interval [CI], 2.5-9.6). Possible publication bias was cited as a limitation.
In the same systematic review, 9 RCTs with 313 patients compared topical antihistamines (levocabastine, azelastine hydrochloride, emedastine, and antazoline phosphate) with placebo. Signs and symptoms (itching, redness, burning, and swelling) were graded using symptom severity scales. Follow-up ranged from 30 minutes to 24 hours. A meta-analysis wasn’t possible because most studies didn’t tabulate the mean scores and error associated with these scores. Most individual studies, however, showed improvement in the cardinal symptom of itchiness.
Finally, 8 RCTs compared topical mast cell stabilizers (sodium cromoglycate, lodoxamide, and nedocromil sodium) with levocabastine, a topical antihistamine. Two RCTs with 74 patients had follow-up periods of 15 minutes to 4 hours; the remaining 6 RCTs with 473 patients had follow-up periods of 14 days to 4 months. Subjective scoring of symptoms was done in 7 of the 8 studies.
Scores between treatment groups were reported as not statistically significant in the 6 longer-term studies. Meta-analysis wasn’t possible because most studies didn’t tabulate the mean scores and error associated with measures. The 2 short-term studies reported a statistically significant reduction in itching and redness (P<.05) in patients treated with the antihistamine (data not provided).