After a number of Apple Watch buyers with tattooed wrists reported that their ink appeared to be interfering with the Watch’s ability to read their heart rates. last Friday, 9 to 5 Mac spotted an update to the company’s support page for the watch that confirms the problem.Apple measures blood flow in part by shining green light — which your red blood absorbs — into your wrist. It then calculates your pulse by tracking how much of that light gets absorbed. But, it seems, the light can have problems getting through tattoo ink to get an accurate reading.
The document says”The ink, pattern and saturation of some tattoos can block light from the sensor, making it difficult to get reliable readings,” . There is no indication from Apple that variations in natural skin tone cause similar problems; the ink seems to be main problem here.
The obvious example is when the watch is too loose and its sensors aren’t in contact with your skin. But Apple said the device can also have problems when it’s being jostled at irregular intervals — such as when you’re playing tennis or boxing — or when it’s cold outside and your blood may be shunted away from the surface of your skin as part of your body’s natural response to lower