McDonald’s food isn't exactly the healthiest choice for kids—and apparently the same can be said of the restaurant’s fitness trackers.

The wristband toys given away in the fast food chain’s signature Happy Meals were intended to help get kids moving. Instead, the toys have gotten company officials racing to issue a recall after the devices were found to burn and irritate kids’ skin. So far, there have been 70 reports of injuries from the colorful gadgets, including seven reports of blistering burns.

On Tuesday, McDonald’s issued a voluntary recall of millions of its “Step It” fitness trackers.

In a notice posted on its website, McDonald’s reported that it did test the trackers previously and added that it is “aggressively investigating this issue.”

“While we do not yet know what may be causing these incidents, we believe it is appropriate to recall these wristbands from consumers in an abundance of caution,” the notice reads.

The “Step It” activity monitors came in two styles: an activity monitor that counts steps and a motion activated light-up band that blinks according to how fast the person wearing it moves.

Parents of kids who received one of the fitness trackers can return it to a restaurant in exchange for another toy, a tube of yogurt, or apple slices.

The company first unveiled the cheap wearables earlier this month as a follow up to previous efforts to improve the nutrition and health of its young patrons. Since 2011, McDonald’s has cut the portion size of fries in its Happy Meals, brought down overall calorie counts, and started offering healthier side options, such as yogurt and fruit. “Physical activity is important to everyone of all ages. We very much support children’s well-being,” according to Michelle McIlmoyle, McDonald’s Canada senior marketing manager.

However, some experts are skeptical of the company’s efforts. "It's a common tactic used by food manufacturers. They promote their products alongside... healthy lifestyles," Jennifer Emond, a pediatrics professor at Dartmouth Geisel School of Medicine, told CNN. This may have the effect of directing parents’ attention away from the low nutritional value of foods.

McDonald’s announced it was discontinuing the fitness trackers on August 17, but it didn’t issue a recall until August 23.