Communication and sensing devices, as well as their respective software, have become versatile for Information Technology (IT) solutions in different contexts. The emergent technology known as the Internet of Things (IoT) has helped both practitioners and researchers to design innovative solutions in healthcare. The IoT-enabled healthcare research is significant due to its valuable implications, including higher quality and lower cost of services and reliable preventive care. This paper reviews the current literature on the IoT in healthcare and discusses its applications and enabling technologies, as well as critical challenges.