All About Eye Allergies
When Ken Hegan traveled to Vancouver a couple of years ago, the city was experiencing one of its warmest Februaries on record, and the trees began showering unwitting visitors with an early blast of pollen. “It felt like my eyes were being assaulted by pollen,” says Hegan.
The filmmaker and humor writer recalls his eyes were red and teary, and this year he’s bracing for the same back home in Toronto.
“Sometimes I wake up and my eyes are caked shut. And when I walk my dog in the morning, I look like I’m crying. My neighbors just think I’m some sad sack guy who cries all the time,” Hegan says with a laugh.
Like millions of fellow allergy sufferers, Hegan’s eyes itch, burn, swell and redden every pollen season, and his vision blurs because of the non-stop tearing. (Others can get such eye symptoms from allergy triggers such as pet dander, mold and dust mites.)
As an avid cyclist, Hegan even fears red lights because when he stops moving, his baby blues well up – and the itch kicks in. “I’m always knuckling away at my eyes. I know I’m not supposed to, but my mom’s not there to tell me to stop,” he jokes.
Despite their mothers’ admonitions to quit that knuckling, people with allergic conjunctivitis – the inflammation of the membrane that covers the white of the eye and the inner eyelid – find that easier said than done.
Pollens’ Chemical Cascade in the Eye
The fact is, they are faced with an annoying and uncomfortable reaction that occurs when pollens or other allergens enter the eye and trigger the same allergic chemical cascade that can occur in the lungs, the nose or on the skin.
Canadian allergist Dr. Harold Kim has a strong interest in eye allergy symptoms. He explains that allergic patients’ eyes contain cells – mostly mast cells – that are primed for allergen exposure. When confronted with the allergen, antibodies called IgE will cause the mast cells to rupture and release chemicals including histamine, one of the main culprits behind the inflammatory response in the eye and surrounding tissues.
For most patients, the resulting symptoms are an annoyance. But the results can be much more serious, especially for those who experience swelling of the conjunctiva itself.
“It looks almost like jelly,” says Kim, who himself suffers from mild eye symptoms during allergy season. “It’s not vision-impairing, but it’s very irritating.”
However, in the most severe cases, the cornea itself can be affected if people don’t resist the temptation to rub and scratch.
“The mechanism is not completely known, but it may be partly from inflammation and partly from scratching, and that can be vision-impairing,” Kim warns. “So those patients should see an opthalmologist and be treated relatively aggressively.”
People who wear contact lenses tend to be even more affected by allergic conjunctivitis, since the contacts themselves are an additional irritant, and they tend to dry the eyes and trap the pollen.
For those patients, it means that when tree or grass pollen season rolls in, the contacts need to come out; and if they suffer from allergic conjunctivitis year-round, eyeglasses may be the way to go.
“It’s sometimes not popular to wear glasses,” says Kim. “But like any inflammatory problem, you really don’t want a foreign body in there, so you have to keep the contacts out.”
The Eyes’ Allergic ‘Reflex’
But while allergy sufferers may feel the symptoms in their eyes, recent studies suggest that in many cases, they’ll need to look beyond their peepers to find significant relief.
According to Dr. Paul Keith, an allergist in the department of medicine at McMaster University, the answer could be literally at the end of their noses.
Keith explains that, when pollen and other allergens enter the nasal passages, the histamine released in the allergic response stimulates nerve receptors, and those receptors can trigger reflex symptoms elsewhere in the body. So while the initial reaction may take place in the nose, patients may actually feel the results in their lungs, on their skin – and in their eyes.
“The mediators stimulate nerve endings within the nose, and send a signal back to the brain. But the brain can’t figure out where it’s coming from,” says Keith.
“So you get signals coming back from the brain that tell the eyes to water and get rid of the problem, even though the problem may not have initiated in the eyes.”
He explains that: “It’s sort of like when you pull a hair from your nose and your eyes water. It’s a reflex mechanism.”
As a result, researchers – some of whom use goggles loaded with pollen to trigger reactions – have found that, in addition to oral antihistamines and allergy eye drops, steroid nasal sprays such as Avamys can be an effective way to get the eyes to chill out. The key to the effectiveness of the medications, says Keith, is to start taking them early.
For instance, if ragweed is a trigger, don’t hold off on the prescription until the tail end of summer.
“It’s really important for people who have problems to take their nasal spray for two weeks prior to the season, so they reduce the number of cells that can react in the nose,” he says. “You don’t get as great an effect if you wait until you’re in the middle of allergy season and get out of control.”
Next: Protecting and treating eyes during allergy season