The specific objective of this study is to determine the stability of immunotherapy extract dilutions. Higher dilutions (lower potency) have been shown in vitro to decrease in potency over time more rapidly than less dilute preparations. The investigators hope to determine whether there is a detectable difference in skin test reaction of dilutions of three common antigens (Cat, Timothy Grass, Dust Mite). The diluents used strongly affect the strength when extract potency is tested in vitro. Therefore, the investigators expect to find a detectable difference in skin test potency based on the diluents used (Saline vs. HSA Saline \[300mcg/ml\]).
