Due to increased number of IoT devices, the marketplace is showing significant growth of sensor deployments around the world. The context involved in any IoT environment needs proper storage, processing and interpretation to get deeper insights from it. Previous research has not focussed much on context-ware security in IoT environment and has primarily relied on context-ware computing methods. In this research paper we implement logical decisions among IoT nodes in healthcare system using ontological approach. With the help of ontological method collected data is transferred between various healthcare devices to the knowledge base thereby achieving security of context like patient data by providing deeper insights, so as to generate intelligent suggested solutions. Incorporation of context-aware rules based on common experience for specific healthcare scenario is done to get implicit insight among IoT nodes.  This work designs security ontology using Security Toolbox: Attacks & Countermeasures (STAC) framework that is implemented in Protégé 5. Moreover, Pellet (Incremental) reasoned is used to evaluate the ontology. Emergency ontology that can prove helpful at emergency times has also been designed.  Different parameters addressed in this work are authentication, access-control, authorization and privacy using context-awareness methodology that can enable naive users make informed security decision.