The following components will be tested to determine their ability to induce a wheal reaction shortly after exposure to the skin by percutaneous application by needle prick: Valortim (Lot# 10-08-001), polysorbate 80, mannitol, histamine (positive control), and saline (negative control). All components except histamine will be provided to the clinical site by PharmAthene with detailed instructions for handling, storage, and dilution. A tiny drop of the aforementioned components will be introduced onto the surface of the skin and the skin will be pricked, allowing the components to enter the surface of the skin. Multiple components will be tested on the subjects' forearms or back; location of testing to be determined by scars, moles,pre-existing skin lesions, or other issues deemed by the Principal Investigator (PI) to have the potential to interfere with interpretation of the results.