Net Charge and Isospin Fluctuations in the World of Elementary Particles

Charge and isospin event-by-event fluctuations in high-energy pp-collisions are predicted within the Unitary Eikonal Model ({\bf UEM}), in particular the fluctuation patterns of the ratios of charged-to-charged and neutral-to-charged pions. These fluctuations are found to be sensitive to the presence of unstable resonances, such as $\rho$ and $\omega$ mesons.We predict that the charge-fluctuation observable $D_{UEM}$ should be restricted to the interval $8/3\le D_{UEM}\le 4$ depending on the $\rho /\pi$ production ratio.This result is shown to be compatible with the formation of a hadron gas at RHIC and SPS energies.