A microstrip based dual-band monopole antenna for body Wearable Wireless Devices (WWD) is proposed utilizing channels in the Ultra Wide Band (UWB) spectrum. The designed dual-band antenna targets lower band (4.7-5.3 GHz) and upper band (7.3-8.5 GHz) of the unlicensed UWB spectrum to meet low, high data rates. The antenna design considers the difference in the interaction of body tissues with the electromagnetic (EM) fields, when compared to free space. The performance of the antenna on different wearable substrates, the robustness of the antenna to work with varying skin thickness and on different sites on the body along with the thermal effects on the skin are analyzed. A simplified, human tissue layer model that is frequency dependent in its properties is used for simulations and computations. Simulated and experimental results were compared and found to be in agreement favouring the use of the antenna for wearable devices for various WBAN applications.