As of May 2015, the Fitbit Force, Charge and Surge models have been reported to cause rashes. Fitbit has acknowledged that the bands on these models may cause a rash and advise consumers to periodically take the device off to prevent it.
Fitbit claims a very limited amount of users have experienced skin irritation. The company has suggested that nickel in the bands may be the cause of the rash, but newer models with reduced nickel content have still caused rashes. Fitbit recommends that users experiencing rashes should remove the band frequently or wear it clipped over a piece of clothing.