The Apple Watch's ability to track a user's health is what makes it more than an accessory that extends the functionality of a user's iPhone. However, early reports have found that the Watch's health sensors seem to be affected by what the wearer has on their body.
Users posted about their watches having a hard time detecting their heart rate through tattoos to Twitter and to Reddit. Tech outlet iMore discovered that while the pigmentation that tattoos create seem to have a negative effect on the sensor, it was only a problem when a tattoo had darker colors.
"Dark, solid colors seem to give the sensor the most trouble - our tests on solid black and red initially produced heart rate misreadings of up to 196 BPM before failing to read skin contact entirely," iMore said. "Tests on lighter tattoo colors including purple, yellow, and orange produced slightly elevated heart misreads of 80 BPM (compared to 69 BPM on the wearer's non-tattooed wrist), but otherwise did not appear to interfere with skin contact registration."
But why is this? iMore notes that it has to do with how the heart sensor tracks heartbeat. "Apple uses various spectrums of light to track the blood flow through your skin. Anything that reduces that light's reflectiveness - ink pigmentation within your skin, for example - can interfere with that sensor." However, iMore notes that this doesn't include natural pigmentation, such as when someone with naturally darker skin uses an Apple Watch.
