New Apple and Samsung phones use infrared light to verify your identity. It's like a hands-free version of the fingerprint scanner. But can the infrared lights used for Face ID and Iris Scanner hurt your eyes?

It's a fair question. People don't know much about infrared light, and it's hard to find information that explains the potential risks of infrared in layman's terms. Not to mention, Samsung's safety disclaimer for the Iris Scanner makes infrared sound kind of scary. But what is infrared, and should we be worried about it?

What is Infrared?

Infrared (IR) is a form of invisible radiation, and it occupies the lower end of the electromagnetic spectrum. Like visible light, microwaves, and radio waves, IR is a form of non-ionizing radiation. It doesn't strip molecules of their electrons, and it doesn't cause cancer.

It's important to know that IR radiation can come from a lot of places. In some ways, you could consider IR a natural byproduct of heat production. Your toaster emits IR light, the sun emits IR light, and campfires emit IR light. Interestingly enough, 95% of the energy produced by fluorescent bulbs is translated into IR. Even your fleshy, disgusting body emits IR light, and that's how the heat-tracking cameras in spy movies work.

The IR-LED that's built into your phone is classified as near IR (700–900 nm). It straddles the line between the visible light spectrum and the IR spectrum. Near IR is very similar to visible light, it's just a lot more difficult for you to see.

The radiation from both visible light and near IR light can heat objects, depending on light intensity and exposure time. Prolonged exposure to high-intensity IR and visible light (staring at the sun or a bright lightbulb) can cause your photoreceptors to bleach and your lens to develop cataracts. To experience vision loss with a low intensity visible or IR light, you would need to keep your eyes open within a millimeter of the light source for almost 20 minutes. This could happen with a light bulb or an IR-LED.

The main concern with near IR is simply the concentration of your exposure. With visible light, it's easy to tell when you're being exposed to a blinding amount, and your reflexes cause you to squint or look away. But your eyes aren't built to see IR light, so it's impossible to tell when you're being exposed to a dangerous amount. You know how you're not supposed to stare at an eclipse, even though it doesn't seem that bright? It's kind of like that.

Far IR radiation (25 - 350 µm) is invisible, and it isn't used in your phone. Far IR radiation overlaps with microwaves on the electromagnetic spectrum, and like microwaves, far IR radiation causes water molecules to heat up. As you can imagine, prolonged exposure to far IR radiation can cause burns to the eyes and skin, but we don't need to worry about that, because your phone only uses near IR radiation.

IR Scanning is Very Simple

Iris Scanner and Face ID are forms of biometric identification, and they're both used to unlock your phone and to open sensitive apps (banking apps, for example). Both processes are similar and easy to understand. New Apple and Samsung's phones are equipped with an IR-LED that emits near IR light, and an IR camera that is capable of capturing IR light.

With Iris Scanning, your Samsung Galaxy illuminates your eyes with an IR-LED and snaps an IR photograph. Then, your phone looks at the details of your eyes and compares them to previous pictures. If the phone can verify who you are, then it unlocks.

But the iPhone X's Facial ID software doesn't just scan your eyes; it scans your whole face. The iPhone X has an IR-LED that's fixed with a dot-matrix mesh. When it turns on, your whole face is illuminated by hundreds of tiny IR dots. The phone takes an IR photo, and that photo is used to verify that the 3D structure of your face matches the phone's settings.

You may have noticed that the IR-LED on the iPhone X is invisible, while the IR light on the Samsung Galaxy is quite blatant. That's because Samsung intentionally pushes its IR-LED as far into the visual spectrum as possible. Believe it or not, the band of IR light that overlaps the visible light spectrum reveals more texture and pigmentation than lower-spectrum IR light.

If you're wondering exactly what area of the IR spectrum Samsung and iPhone are working with...well, we don't know any exact numbers. The Samsung Galaxy and the iPhone X spec pages don't even mention IR-LEDs. But knowing that the IR cameras in your phone need to pick up a lot of detail to make verification efficient, it's probably safe to assume that they occupy a wavelength between 870 nm and 950 nm---the overlapping point between near IR and visible light.

Also, biometric paperwork by Renesas classifies the IR-LEDs in phones as "low-risk" IR. By OSHA standards, low-risk IR products are not powerful enough to heat your eyes, and they aren't capable of causing eye damage under normal use.

There Are Some Popular Rumors About IR, and They Aren't True

When you Google "IR iris scanner," you'll find a lot of people asking whether or not IR light can hurt your eyes. And that's a fair question. Most people don't know anything about IR, and Samsung's scary Iris Scanner disclaimer warns that epileptics, children, and people that experience fainting should avoid using the Iris Scanner. (Interestingly, Apple's Face ID disclaimer makes no such warnings.)

Your Google results will also show you a lot of misinformation that's been posted by Reddit users and bloggers. News and tech websites mindlessly pick up on this nonsense, which makes it difficult to find accurate information about the IR scanner in your phone. Whether accurate scientific information suggests that IR is safe or dangerous is beyond the point. Blatant misinformation is bad for everyone, so we're going to take a moment to squash some rumors.

Let's get the big one out of the way. IR doesn't cause cancer. IR is a form of non-ionizing radiation, which means that it can't strip molecules of their electrons and it can't cause cancer. X-rays, gamma rays, and high-frequency ultraviolet light (stronger than a blacklight) are forms of ionizing radiation, and they can cause cancer. Anyone who tries to tell you that radio waves, microwaves, or IR light causes cancer has no idea what they're talking about.

Another big misconception that's floating around is that the IR LED in your phone is a laser. It isn't. Lasers are a narrow wavelength of light, and they move in a single direction. The lights on your phone occupy a broad wavelength. They're also diffused by lenses and filters because they need to be able to illuminate your entire face.

Finally, a scientific paper about the effects of IR radiation on the eyes of rabbits has been floating around, and it's scaring a lot of people. Essentially, rabbits were exposed to IR light, and they developed lens damage and cataracts. But if you take a minute to read this paper, it's clear that you can't apply these results to the use of IR scanners in phones.

First off, the scientists in this study used large lamps to expose the rabbits' eyes to light, and they performed these exposures for 5 to 10 minutes at a time. The IR light in a Samsung or Apple phone is smaller than an ant, and it only lights up for 10 seconds at a time. Also, the IR lights used in phones only utilize the near IR frequency. The lamps used on the rabbits emitted light from the UV frequency, the visible light frequency, the near IR frequency, the mid IR frequency, and the far IR frequency. As you're probably aware, UV light is strong enough to cause sunburns, and far IR light is similar to a microwave and causes water molecules to heat up.

So, Are There Health Concerns?

Okay, so we've cleared the air of some nonsense, but Samsung's scary disclaimer isn't going away. Even though consumer IR devices have been on the market for a long time, and there are strict regulations in place for IR-LEDs, this is the first time we've had a product that routinely shoots IR light into peoples' eyes. How can we be sure that technology is safe?

According to Renesas and Smartvisionlights, less than 10 seconds of visual exposure to near IR is classified as low risk. For the IR-LED in your phone to cause immediate damage to your eye, you would have to hold it 1mm away from your eye for 17 unbroken minutes. It isn't possible to do this with a Galaxy or iPhone X, as both products limit IR exposures to 10 seconds, and they won't emit IR light unless the device is 20cm from your head.

These papers also mention that "abnormally photosensitive individuals" are at a higher risk to eye damage due to near IR light. It's interesting to note that the exposure limits set for IR-LEDs don't take "abnormally photosensitive individuals" into consideration, so it's possible that the IR-LED in your phone could hurt your eyes if your eyes are abnormally photosensitive. Of course, if you're abnormally photosensitive, then you'd probably be aware of that by now. Going outside on a sunny day would be a nightmare.

As Samsung's health warning states, people with epilepsy or other light-triggering conditions shouldn't use the IR-LED. This warning exists to help people avoid passing out or having a seizure; it has nothing to do with vision loss. If you don't have a medical condition that's triggered by light, then you don't have to worry about this.

We should also take into account some new research which suggests that occasional exposure to low-risk IR light is actually beneficial to the eyes. These exposures aren't long enough or intense enough to increase the temperature of your eye, and they may encourage cells to heal damaged tissue. Some scientists are experimenting with IR-LED's as a form of eye therapy, and these LEDs are about the same intensity as the IR-LED in your phone.

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From what we know right now, we can be pretty sure that Iris Scanner and Face ID won't hurt your eyes. But nothing's for certain. Even though modern scientific studies show that low-risk IR products are harmless, nobody's tested the effects of daily exposure over a span of, say, 30 years.

If you're concerned that the IR light from your phone is bad for your eyes, then you may as well turn it off. That being said, there's a very good chance that everything's okay.

Sources: INCIRP, NCBI, COGAIN, Dovepress, Renesas, Smartvisionlights