The growth of IoT has led to a surge in connected devices and data production in the medical field. To meet the increasing demand for modern healthcare, Fog and Cloud services assist IoT-based equipment. Securing data as it travels through multiple levels is challenging. The CP-ABE cryptographic approach enables efficient access control, but existing schemes do not support attribute unification in multi-authority setups. We propose SMAC, a multi-authority CP-ABE scheme that introduces attribute unification. By outsourcing costly encryption and decryption to fog, SMAC reduces the computational overhead for resource-constrained users. Our security and performance evaluation confirms that SMAC is a secure, efficient access control mechanism for IoT devices.