CEO and co-founder James Park says about 1.7 percent of users reported skin irritation in a letter posted on the company website Thursday.
Fitbit says independent test results have not found problems with the Force's battery or electrical systems and suggests that users may have had allergic reactions to nickel in the device or materials used in the strap or adhesives used to make the Force.
The company is offering a full refund.
The Force can track steps taken, stairs climbed and calories burned. FitBit also makes other fitness wristbands and devices.
