What Pataday is
Pataday Once Daily is the brand name for olopatadine 0.2% eye drops, made by Alcon. Olopatadine is a "dual-action" drop. It blocks histamine at H1 receptors to stop itching that has already started. It also steadies mast cells, the cells that release histamine, so less is released the next time pollen or dander lands on your eye PMID: 30020258.
The item we link to is a 2-pack of 2.5 mL bottles. The dose is one drop in each affected eye, once a day.
How well it works
Antihistamine and mast-cell-stabilizer eye drops are among the best-supported allergy treatments you can buy without a prescription. A Cochrane review of 30 trials found that all the drops it studied, olopatadine included, reduced the symptoms and signs of seasonal allergic conjunctivitis compared with placebo. It also noted that the trials were short and there's little long-term data PMID: 26028608.
The 0.2% strength has its own trial. In a 10-week study during grass pollen season, once-daily olopatadine 0.2% cut both itching and redness compared with placebo, and it was well tolerated PMID: 15476905.
What it treats well: itchy, watery, red eyes caused by pollen, dust mites or pet dander.
What it doesn't treat: dry eye, eye infections, or redness from smoke, chlorine or lack of sleep. If your eyes are red but not itchy, allergy may not be the cause.
Side effects and safety
Olopatadine drops are generally well tolerated. The Cochrane review found no serious side effects linked to this class of drops PMID: 26028608. Some people notice brief stinging or a mild headache.
Practical tips from the label:
- Remove contact lenses before using the drops. Wait at least 10 minutes before putting them back in.
- Don't touch the dropper tip to your eye or anything else. This keeps the bottle clean.
- See a clinician if you have eye pain, vision changes, or redness that gets worse or doesn't improve. Those aren't typical allergy symptoms.
Skip "get the red out" drops for allergies. Products with tetrahydrozoline or naphazoline shrink blood vessels. They hide redness but don't treat the allergy. Some can stop working as well with continued use and cause rebound redness when you stop PMID: 32801982. Chronic redness caused by the drops themselves has a name: conjunctivitis medicamentosa PMID: 8027493.
Pataday vs. Zaditor
Zaditor (ketotifen 0.025%) is the other main over-the-counter dual-action drop. Both work. The differences are modest:
- Redness: a meta-analysis of seven randomized trials found olopatadine led to significantly less eye redness than ketotifen. It found no significant difference in itching, tearing or papillae PMID: 37312902.
- Speed: in one 120-patient randomized trial, olopatadine relieved itching, tearing and redness faster than ketotifen and caused fewer side effects (10% vs. 18%). That trial used the older 0.1% strength of olopatadine PMID: 29719638.
- Dosing: Pataday is once a day. Zaditor is every 8 to 12 hours, no more than twice a day.
- Price: Zaditor usually costs less per month.
Alcon also sells a stronger 0.7% version of olopatadine. In an allergen-challenge trial, the 0.77% strength relieved itching better than 0.2% at 24 hours PMID: 26266427. It's a different product from the one we link to.
Who should buy it
Buy Pataday if your main symptom is itchy, watery eyes and you want one drop a day. It's also a good add-on if an allergy pill like Zyrtec handles your nose but not your eyes.
Buy Zaditor instead if price matters more than convenience and a second daily dose isn't a problem.
Add Flonase if a stuffy nose is part of the picture. See our full Best Eye Drops for Allergies ranking for more options.