  The retarded dispersion interaction (Casimir interaction) between two dilute
dielectric media at high temperatures is considered. The excited atoms are
taken into account. It is shown that the perturbation technique can not be
applied to this problem due to the divergence of integrals. A non-perturbative
approach based on kinetic Green functions is implemented. We consider
interaction between two atoms (one of them is excited0 embedded in an absorbing
dielectric medium. We take into account possible absorption of photons in the
medium, which solves the problem of divergence. The force between two plane
dilute dielectric media is calculated at pair interaction approximation. We
show that the result of quantum electrodynamics differs from the Lifshitz
formula for dilute gas media at high temperatures (if the number of excited
atoms is significant). According to quantum electrodynamics, the interaction
may be either attractive or repulsive depending on the temperature and the
density numbers of the media.
