Fitbit, the company that sells wireless activity trackers, has announced a voluntary recall of its Fitbit Force device. Popular with individuals aiming to walk (or run) 10,000 steps per day or to achieve other activity-related fitness goals, Fitbit devices not only act as pedometers, but can also synchronize information from the device to a user's profile on Fitbit.com. The recall comes after weeks of reports of rashes experienced by Fitbit Force wearers.
The Fitbit Force looks like a bracelet, and includes nickel components, which may be the trigger for allergic contact dermatitis in some users, according to CEO James Park. Doctors at UC-San Diego call allergic contact dermatitis (ACD) a "type IV delayed hypersensitivity reaction." As a team of Japanese researchers explain in their paper on metal allergy, "Metal allergy is thought to be caused by the release of ions from metal materials." Nickel is an interesting choice of material for an activity tracker designed to be worn virtually 24 hours per day -- the Fitbit Force also functions as a sleep tracker -- as nickel is a "well-known causal agent of allergic contact dermatitis."
Additionally, the wristband portion of the Fitbit Force is made of silicone, a synthetic compound containing the tetravalent metalloid silicon. Although silicone is generally believed to have low toxicity, sensitization and allergic reactions to silicone have been noted in medical literature. In fact, ACD reactions to silicone-based cell phone covers are a growing concern among dermatologists. Broadly speaking, wearing a silicone-based, nickel-containing bracelet all day, every day seems like a risky proposition for at least some portion of the population.
Fitbit Force users who would like to receive a refund are instructed to fill out a form to request a return kit. A wiser choice for consumers concerned about a potential ACD may be the Fitbit Zip, which clips on to clothing and can be worn in such a way that it does not touch the skin.