Last Updated: March 2026 | Reviewed by Dr. Davinder Sidhu, OD
Tree pollen doesn't just make your eyes itch. It triggers an inflammatory response that sticks around for hours after you go back inside, and over time, it damages the glands that keep your tears stable. That's why allergy season and dry eye are so tangled up for most people.
What happens when pollen gets in your eye?
Twenty minutes. That's how fast it takes to feel it.
Birch pollen (or alder, or cedar, depending on where you are) lands on your conjunctiva and your mast cells dump histamine, prostaglandins, leukotrienes, and a pile of inflammatory cytokines all at once. Itching, redness, watering, swelling.
From 4 to 24 hours after that first hit, eosinophils and T-cells show up in the conjunctival tissue and keep the inflammation running long after the pollen is gone. I had a 34-year-old project manager from North Vancouver in last April. Walked her dog for maybe 20 minutes on a Saturday morning. By Saturday night she couldn't keep her eyes open. She was having a bad allergy day. Her eyes were in a late inflammatory response. The pollen was long gone, but her immune system wasn't done yet.
How does pollen damage your meibomian glands?
A retired school librarian from Kelowna had "bad allergies" every April for as long as she could remember. Rubbed her eyes constantly. Never thought much of it. When I did her meibography, her gland imaging looked like someone 15 to 20 years older. More than half the glands in her lower lids were just gone.
Your meibomian glands sit along your eyelid margins and produce the oil layer that stops your tears from evaporating. Pollen triggers inflammatory cytokines (IL-4, IL-5, TNF-alpha). They go after the ductal cells of the meibomian glands directly.
A 2022 study in the Journal of Clinical Medicine compared 89 seasonal allergy patients against 112 controls:
| Measurement | Allergy Patients | Healthy Controls |
|---|---|---|
| Dry eye present | 92% | 29% |
| Meibomian gland dropout (visible on imaging) | 61% | 27% |
| Tear breakup time (shorter is worse) | 5.2 seconds | 8.4 seconds |
| Tear evaporation rate compared to baseline | 3x higher | Normal range |
Ninety-two percent.
Three things happen. First, inflammatory mediators thicken the epithelial lining of the duct openings (hyperkeratinization), which plugs them. Second, all that eye rubbing compresses and distorts glands embedded in thin eyelid tissue. Third, blocked glands can't release oil. The oil backs up, the gland swells, and acinar cells atrophy.
Once a gland is gone, it's gone. There's no growing it back. That's what makes this different from regular allergy symptoms. The itch goes away in June. The gland damage doesn't.
(This is also why I get a little intense about lid hygiene during pollen season. But more on that later.)
When does pollen season actually start in Canada?
Earlier than you think, and it's changing each year.
A Proceedings of the National Academy of Sciences analysis across the U.S. and Canada found that pollen seasons now start 20 days earlier than they did in 1990, it runs 10 days longer, and carry 21 percent more pollen.
We are lucky though to experience spring in Canada, here is a rough guide to see the season in all its beauty:
- Coastal BC: Cedar and juniper pollen can show up late January. Alder by March. Birch mid-April. If you're in Vancouver or Victoria, you're dealing with pollen before most Canadians have put away their snow boots.
- Ontario: Red maple starts in March, birch first week of April, peaks late April. Oak and elm carry it through May and June.
- Prairies: Late April to early May for birch. Spruce and pine pick up in June.
Why eye drops alone isn't enough
A 2022 review across nine studies and over 7,000 patients found that 47 percent of allergic patients also have dry eye disease. Nearly half. Most of them are only treating the allergy side.
Oral antihistamines like diphenhydramine (Benadryl) actually reduce your tear production. One study showed a drop of 4.58 mm on the Schirmer test compared to placebo. The anticholinergic mechanism suppresses both your aqueous tears and mucin production. You're treating the itch while making the dryness worse.
Even second-generation antihistamines like loratadine don't touch the meibomian gland damage. The meta is to combo treatment.
Antihistamine (topical or oral) is perfect for the allergic inflammation.
A preservative-free eye drop like Thealoz Duo works to stabilize the tear film.
Lid hygiene is overlooked. Blephaclean wipes remove pollen residue and bacterial biofilm from the lash line.
A preservative-free lubricant for heavy days. I-Drop Pur uses a viscoadaptive formula that stays on the eye longer without blurring.
Treat it as a dry eye problem that happens to also involve allergies. Not the other way around.
Can you prevent the damage before pollen season starts?
Not all of it. But you can reduce how much ground you lose.
Start a lid hygiene and artificial tear routine two to three weeks before your regional pollen season begins. Windows closed on high-count days. Shower and change when you come in. And wash your pillowcases more often than you think you need to. Pollen accumulates on your pillow case and transfers to your lids overnight.
What about contact lens wearers?
Your lens surface collects pollen deposits all day, keeping the allergen sitting directly on your conjunctiva for hours, it can be quite uncomfortable.
Use a preservative-free rewetting drop, not a preserved one. And if your lenses become genuinely uncomfortable, take them out. I know that's not what people want to hear. But pushing through lens discomfort during allergy season is how people end up with corneal complications that last longer than pollen season does.
Frequently Asked Questions
Can seasonal allergies cause permanent dry eye?
Yes. The gland damage doesn't reverse.
Should I use allergy drops or artificial tears?
Both. They do different things. Antihistamine drops block the allergic response. Artificial tears stabilize the tear film the allergic response has disrupted. Using one without the other leaves half the problem untreated.
When should I start preparing my eyes for allergy season?
Two to three weeks before your regional pollen season. Coastal BC: mid-January. Ontario: mid-March. Prairies: early April.
Do warm compresses help with allergy-related dry eye?
A study from Harvard's Schepens Eye Institute found five minutes of warm compress increased tear film lipid layer thickness by over 80 percent. That lipid layer is exactly what meibomian gland dysfunction destroys. A nightly warm compress during allergy season is one of the most effective things you can do.
Is it allergies or dry eye? How do I tell?
Itching is allergy. Burning and grittiness is dry eye. If you itch AND burn, you probably have both. A dry eye assessment from your local optometrist can show what's going on structurally.
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About the Reviewer
Dr. Davinder Sidhu is an optometrist based in British Columbia with a focus on dry eye management and preservative-free solutions. Learn more at TheGenuwineOD.com or follow him on Instagram and Facebook.
