 The hygiene hypothesis suggests that the absence of endotoxin exposure leads to an unfavorable Th1Th2 balance. A controlled antigen exposure during infancy may help establish a Th1 Th2 balance that blocks the onset or progression of asthma. Lactobacillus is a bacterium found in many foods in the typical pediatric diet, and is used as a supplement to prevent diarrhea. Due to the safety, feasibility, and early promising results in preventing atopic dermatitis, Lactobacillus is an ideal bacterium to use as an exposure to test the hygiene hypothesis. The investigators hypothesize that such an exposure may block or delay development of early markers of asthma. 