The use of topical ocular antihistamine/decongestant combinations to treat symptoms associated with allergic conjunctivitis is widespread, effective, and generally without adverse effects. Recently, these medications have become available without a prescription, possibly leading patients to the erroneous assumption that they are void of side effects. Likewise, patients may use these drugs for many ocular therapies for which they are unintended, possibly resulting in ocular complications. One significant adverse effect of these antihistamine/decongestant combinations when used inappropriately is pupillary dilation with associated blurry vision. Continued emphasis of the possible deleterious side effects by the clinician is recommended to circumvent these problems.