The van der Waals interaction energy is derived for a homogenous fluid of polarizable particles. Low-temperature corrections to the van der Waals interaction energy are computed numerically for three cases: Dilute media with radiative interactions, arbitrarily dense media without radiative interactions, and arbitrarily dense media with radiative interactions. The validity of the model used to calculate the corrections at arbitrary densities is argued for, by comparison with the results for low densities.