Minimizing Adverse Skin Reactions to Wearable Continuous Glucose Monitoring Sensors in Patients With Diabetes

The promise of technology for disease management is being delivered to people with diabetes. Pumps for continuous subcutaneous insulin infusion (CSII) and continuous glucose monitoring (CGM) systems are all available as wearable devices. Most commonly used are CGM systems, either classic real-time CGM (rtCGM) or flash glucose monitoring (flash).

CGM systems provide their users with continuous information on their glycemic status that is associated with lower glycated hemoglobin (HbA1c) and reduced time in hypoglycemia, ¹ as well as greatly reducing the burden of frequent finger-prick self-monitored blood glucose (SMBG) testing. The flexibility and freedom provided by wearable CGM devices are achieved in part by skin-adhesive patches, which must be strong enough to survive during everyday activities for the wear time of each sensor device. In the case of most rtCGM devices, this is 6 or 7 days, whereas flash devices have a 14-day wear time. As the number of people using these systems has grown, so has the number who have experienced adverse skin reactions at the site of the device placement because of sensitizers present at the adhesive site or associated with the plastic device housing. Such skin reactivity is a serious consequence and may lead to a person with diabetes discontinuing usage of the device. ² This is undesirable since these wearable devices can significantly improve glycemic outcomes and quality of life for people with diabetes. ³

Dermatologists ultimately identified isobornyl acrylate (IBOA) as the major skin sensitizer present in wearable glucose monitoring devices. ⁴ Significantly, cases of skin sensitivity in this context were reported for the FreeStyle Libre glucose monitoring system, which has a comparatively large user base. By changing its manufacturing processes, Abbott has been able to remove IBOA from its FreeStyle Libre product. As of July 31, 2020, IBOA is no longer present in FreeStyle Libre, FreeStyle Libre Pro, or FreeStyle Libre H devices shipped worldwide. IBOA has never been present in FreeStyle Libre 2 or FreeStyle Libre 3. Health care professionals may contact local Abbott representatives to confirm when the supply of sensor devices available in their respective countries is IBOA-free, especially before considering use in individuals with known IBOA sensitivity. A recent publication by independent researchers has confirmed that FreeStyle Libre 2 does not contain IBOA. In addition, they observed that patients with known IBOA sensitivity tolerated this new system without IBOA. ⁵

Other acrylates, such as ethyl cyanoacrylate, have been implicated in contact sensitivity to rtCGM devices of other manufacturers, ⁶ which has resulted in manufacturing changes by Dexcom to reduce the risk of associated skin reactivity.

The value of wearable CGM systems in diabetes care is accepted, but early generations included the risk of adverse skin reactions for a number of users, particularly when using devices with longer skin-contact periods. The identification of IBOA as a major cause of skin contact sensitivity has been a significant step toward eradicating these reactions. Learnings from the first generations of CGM devices have ensured that significant skin sensitizers, such as IBOA and other acrylates, have been removed. This ensures that the health benefits of CGM systems are accessible to the widest possible community of people with diabetes.