
A growing number of users have turned to social networks claiming that full sleeve tattoos, ones that stretch to cover the wrist, interfere with the Apple Watch's heart rate sensor and skin contact registration. Consequently, some Apple Watch users with tattoos have been unable to receive notifications and are frequently prompted to re-enter their passcode, if one is set, on the wrist-worn device.

The severity of problem appears to depend on the color and ink saturation of the tattoo, with darker, solid tattoos causing the most interference with the Apple Watch's sensors. A temporary solution for affected users is to toggle off Wrist Detection in the Apple Watch app under the General menu on the main settings tab, but doing so will disable Apple Pay from being used on the Apple Watch."So I thought my shiny new 42mm SS watch had a bad wrist detector sensor," writes Reddit user guinne55fan. "The watch would lock up every time the screen went dark and prompted me for my password. I wouldn't receive notifications. I couldn't figure out why especially since the watch was definitely not losing contact with my skin. also I couldn't find anything online with people experiencing this issue. I was about to give up and call Apple tomorrow when I decided to try holding it against my hand (my left arm is sleeved and where I wear my watch is tattooed as well) and it worked. My hand isn't tattooed and the Watch stayed unlocked. Once I put it back on the area that is tattooed with black ink the watch would automatically lock again."
Article Link: Some Tattoos Found to Interfere With Apple Watch's Sensors