In this paper, we propose a simple, but accurate propagation model through the skin based on a
distributed-parameter circuit that leads to the obtaining of simple and general attenuation expressions for both galvanic and capacitive coupling methods that could assist in the design of Intra-body Communications (IBC) systems. The objective of this model is to study the influence of the skin impedance in the propagation characteristics of a particular signal. In order to depict that skin impedance, the model is based on the major electro-physiological properties of the skin, which also allows a personalized model. Simulation results have been successfully compared with several published results, thus showing the tuning capability of the model to different experimental conditions.