The goal of the present study was to evaluate alterations to regulatory T cell (Treg) populations following antibiotic treatment. To examine this, we orally treated mice with Erythromycin and dissected the spleen and mesenteric lymph nodes. Tregs were isolated and enumerated by flow cytometry. Mice were then treated with OVA to induce oral tolerance, but tolerance could not be demonstrated. It was established that oral treatment with Erythromycin does not influence total CD4+ or Treg numbers.