Studies of the effects of yogurt on immunity and atopic diseases have suggested improvements in cytokine (interleukin-2 and interferon-gamma) responses and clinical scores in patients with allergic rhinitis. This study compares prospectively immune parameters of participants who received 16 oz of yogurt versus 16 oz of milk/day in a randomized cross-over design. Yogurt that contained live, active Lactobacillus bulgaricus and Streptococcus thermophilus or 2% milk was consumed for one month each. Twenty otherwise healthy adults with atopic histories documented by skin testing were enrolled. Immune studies were performed at the beginning and end of the two 1-month study phases, separated by a 2-week washout period. These studies included measurements of cellular, humoral, and phagocytic function. No adverse events were noted in either group. No significant improvements in any immune parameter were noted. The consumption of yogurt that contained the live active bacteria L bulgaricus and S thermophilus does not appear to enhance immune function in atopic individuals at the dosage and duration used in this study.