A "small number" of Fitbit Force customers are reporting an odd skin irritation after wearing the fitness tracker. The Fitbit Force is designed to be worn 24/7, even while sleeping, so it's definitely a cause for concern.

The Consumerist was the first to highlight the issue from several readers who noticed a red blotch forming on their skin under the device where the battery and charging port sits. Other users have reported the same on a Fitbit forum thread dedicated to the problem.

Fitbit has acknowledged the issue, and is offering a full refund or the option for customers to switch out for a different tracker within the Fitbit line.

"We are aware that some of our customers have reported a skin irritation from wearing their Force device," Fitbit said in a statement. "We conduct testing in order to satisfy a variety of internationally accepted standards relating to the safety of the materials in our devices. Fitbit wristbands are made of an elastomer material similar to many sports watches and do not contain latex."

You may expect a rash to form after wearing anything on your skin over a long period of time, but if you go over to The Consumerist and don't mind seeing what isn't a normal skin rash, you'll understand why a few users are upset. It's not clear if allergies are the cause, or if there is something else at play. Fitbit hasn't said there is a problem with its device.

"Our customers are our top priority, so we already have been taking steps to make this right with any customers who feel that they have an allergy related to their Fitbit device including offering a refund or a choice of a replacement tracker," Fitbit wrote. "Fitbit will handle all shipping costs and will provide a refund in any difference in price."