Apple Confirms Watch's Aversion To Dark Tattoos, Recommends Using External Heart Rate Monitor

Apple has acknowledged that some skin tattoos and other factors can affect the ability of an Apple Watch to detect a person's heart rate. The issue came to light recently when some Apple Watch owners began complaining that their wearable wasn't functioning properly when worn on top of a tattooed wrist, which seems to be exacerbated by darker tattoos.

The reason for this has to do with the way Apple Watch devices read heart beats. Apple's wearables are equipped with LED lights paired with light-sensitive photodiodes that can detect the flow of blood in your wrist at any given time. It does this by flashing its green LED lights hundreds of times per second, which allows it to calculate the number of times the heart beats each minute. Buy why use green LEDs? Your blood is red because it reflects red light and absorbs green light.

Apple Watch LEDs

"Permanent or temporary changes to your skin, such as some tattoos, can also impact heart rate sensor performance. The ink, pattern, and saturation of some tattoos can block light from the sensor, making it difficult to get reliable readings," Apple explains in an updated support document.

In addition to certain tattoos, Apple says that skin perfusion and motion are two other things that can prevent the Apple Watch from obtaining accurate readings. Unfortunately, Apple's solution to these scenarios isn't all that great -- the company suggests investing in a wireless external heart rate monitor such as Bluetooth chest straps.