Apple has confirmed that permanent or temporary changes to the skin like tattoos can lead to inaccurate readings in Apple Watch.
According to the Verge, Apple said that the tattoo ink, pattern and saturation can block light from the sensor, making it difficult to get reliable readings.
However, Apple did not suggest what type of tattoos will pose a problem and which ones will not.
Apple suggested that darker tattoos cause major issues that prevent the Watch's light from getting through.