Wrist Tattoos & The Apple Watch Don't Mix

Photographed by Lauren Perlstein.
Your fashionable, fabulous ink could mess up your Apple Watch experience. 

The Apple Watch has a skin sensor on the back that uses infrared and green LEDs to detect your heart rate. When the watch senses that it's not next to skin anymore, it requires you to enter a passcode before it will let you access notifications or any other watch features. Early wearers who also have tattoos on the top of their wrists, where the Watch sits, report difficulty receiving notifications on the Watch; it's behaving like it's not making skin contact, thus requiring the wearer to enter a passcode. That's annoying.

Reddit user guinne55fan explains:

The watch would lock up every time the screen went dark, and prompted me for my password. I wouldn't receive notifications. I couldn't figure out why... I decided to try holding it against my hand (my left arm is sleeved and where I wear my watch is tattooed as well) and it worked. My hand isn't tattooed, and the Watch stayed unlocked. Once I put it back on the area that is tattooed with black ink, the watch would automatically lock again.

The problem seems to lie with the Watch's green LEDs, which shine light into the skin to illuminate capillaries and measure heart rate, according to Quartz. Normally, this light can break through the first few layers of skin, but if those layers also contain tattoo ink, the green light gets absorbed before it reaches your capillaries, fooling the Watch into thinking that it's not sitting on skin at all.

Apple is not the only company to use this green-LED-based technology in its heart-rate sensing; The Fitbit Surge also uses this method, as does the Basis Peak

iMore performed extensive tests and found that the watch's sensors go bananas on areas of skin with dark, solid ink. A lighter-colored tattoo, line-based graphics, and text shouldn't cause as many issues (a tattoo on the side of the wrist, like in the photo on this article, would not cause problems at all). 

Dark skin tones will NOT have an adverse affect on how the sensor performs. In a study examining light reflectance with regard to light wavelength and skin types with varying degrees of melanin (which causes dark pigmentation), a study from the University of Texas concluded that "there was no significant interaction between the wavelength of light and the skin type." 

If your wrist is heavily tattooed and you plan to wear an Apple Watch, you can get around the main issue (that it thinks it's not on skin and locks itself) by switching off Wrist Detection in the Apple Watch iOS app. Caveat: This will also prevent Apple Pay from being used on the watch. Alternatively, you can just strap it on a non-tattooed wrist instead. Who wants to hide that awesome ink anyway?
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