Shortly after the news that tattooed wrists can prevent the Apple Watch’s heart rate sensor from functioning properly went viral, Apple has updated its user guide, confirming that wrist tattoos may interfere with the heart rate monitor. Long-term and temporary changes to human skin, including the ink used in tattoos, may affect the heart rate sensor’s performance, according to Apple.
Moreover, the updated Apple Watch support documentation explains that the ink, pattern and saturation of the tattoo can block the green and infrared light from the sensor, which is absorbed or reflected by red blood, making it difficult for the device to calculate reliable readings. Watch wearers with darker tattoos that cover more of the skin`s surface may face more problems compared with those whose tattoos are lighter and smaller in size.
Actually, solid-colored tattoos, especially red ones, absorb the green light the watch gives out to read out the heart rate, thus making the heart rate monitor useless. Moreover, the device uses the heart rate monitor to determine whether you are wearing it or not. If the watch fails to detect that you’re wearing it, the screen locks with your passcode. Many watch wearers are also unable to use Apple Pay as a result of interference from their tattoos. Due to security reasons, Apple Pay only works when the watch is being worn.
Not only Apple Pay, but various other applications are not working either, and many users are having problems with even simpler functions. Especially they can`t check the watch through wrist movements.
Apple recommends those who experience such kind of problems to unable wrist detection entirely and connect Apple Watch wirelessly to external heart rate monitors, like Bluetooth chest straps. Apparently, it`s not quite elegant solutions, but at least athletes and more serious self-enthusiasts will get an alternative means of collecting this data.