When the sky starts to turn smokey, your eyes start to itch and the air quality alert goes off on your phone, you probably reach for the cabinet to grab some allergy medicine. But that might not be the best solution.

Even though it may feel like the right move.

Smoke irritates your nose and eyes. Antihistamines fix irritated noses and eyes. But the medicine you grab matters.

Choosing the right medicine

Diphenhydramine, the active ingredient in Benadryl, dries out your mucous membranes. Those membranes are the primary mechanism your body uses to trap and clear inhaled particles like smoke. 

When you dry them out, you are degrading your first line of defense when you need it most. 

If you want an antihistamine for smoke symptoms, reach for a second-generation one instead, like cetirizine (Zyrtec) or loratadine (Claritin). They address the same symptoms without the drying effect.

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Smoke isn’t technically an allergen

Wildfire smoke isn’t an allergen. Technically it’s an irritant, so it doesn’t invoke an immune system reaction. 

But it does trigger the same histamine response in your nasal passages and airways. 

Your body’s reaction looks like an allergic reaction even though it isn’t one, which is why an antihistamine genuinely does help with the sneezing, runny nose and itchy eyes. 

Allergy medicine doesn’t treat the actual threat

Allergy medicine treats your symptoms. But it does not protect your lungs or heart. It does nothing to help the actual threat in wildfire smoke.

Smoke consists of PM2.5, fine particulate matter that is 2.5 micrometers or smaller. That’s roughly 30 times smaller than a strand of hair. 

They are small enough to bypass your upper airway’s defenses entirely, traveling deep into the lungs and bloodstream. It can drive oxidative stress, lung inflammation and elevated risk of cardiovascular events. 

(FORECAST: Northwest wildfire smoke blankets Seattle, Portland)

Even a short-term exposure to PM2.5 can have a range of outcomes, anywhere from minor irritation to heart failure. 

The danger of using allergy medicine during smoke events is that you start to feel better, but the threat is still there. 

Your sneezing stops, your eyes stop itching and you feel fine. But that still doesn’t mean you should go outside, because the PM2.5 will still enter your lungs at the same rate as before. Except now you have no symptoms reminding you to go back inside. 

The CDC advises that regardless of how you feel, staying indoors is the best way to protect yourself during wildfire smoke episodes. 

If you must go outside, wear a properly fitted, NIOSH-approved N95 or P100 respirator — they’re the only thing that filters PM2.5.

Miriam Guthrie is an associate meteorologist with weather.com who graduated from Georgia Tech with her undergrad and graduate degrees in Earth & Atmospheric Sciences.