There are many ionizer air purifiers available on the market today. These devices work by using charged ions to make airborne particles stick to surfaces, which helps the particles get captured more easily by filters. A big downside of ionizers is that they cause particles to stick inside our lungs! That means ionizers might make people more likely to get infected.

Researchers in Italy tested this by having participants breathe particles with a more or less electrostatic charge. They measured the number of particles in the air before people breathed it and after they breathed it out. That way, they could tell what percentage of particles stuck in people’s airways. As the electrostatic charge increased, a higher percentage of particles stuck inside the participants.

So ionizers might help because they make particles stick to the walls and other surfaces in your home more. That would keep the particles out of your lungs. But they might hurt because virus particles you breathe in are more likely to stick inside your lungs.

So what’s the net effect? Does the harm outweigh the benefit? I haven’t seen a study testing it.

Ionizers May Cause More Inflammation

To add another layer on top, a study found that breathing air from ionizing purifiers caused more inflammation in people’s bodies. Researchers had (very brave) volunteers breathe (1) straight diesel exhaust or (2) diesel exhaust cleaned by an ionizer air purifier.

Then they measured the inflammation in people’s bodies. Breathing the air from the ionizer purifier actually led to more inflammation in people’s bodies.

It’s speculative, but the inflammation may make our bodies more susceptible to infection. Or it might make those infections worse. The uncertainty alone is enough to make me wary of using an ionizer to prevent infection.

Clean Air Without the Side Effects

A better way to build a purifier is to capture the particles in the purifier, not in our lungs. An easy way to do that is to use a filter, like a HEPA filter. HEPA filters capture particles inside the filter.

The researchers in the inflammation study did just that. People who breathed the diesel exhaust cleaned through a HEPA filter experienced less inflammation in their bodies. That’s how it should be!

I should make it clear that I’ve never seen a test of ionizers on actual infection rates in humans. So these mechanisms are theoretical, not proven. But they’re enough to give me pause.