Desensitization of Human Mast Cells: Mechanisms and Potential Utility for Preventing Anaphylaxis

Inclusion Criteria: * Written informed consent obtained. * Male, or non-pregnant female, 18-45 years of age who are in good health. * Clinical history of a penicillin allergy consisting of an immediate hyper- sensitivity reaction such as anaphylaxis, urticaria/angioedema or broncho- spasm, and a positive skin prick test to penicillin G. * Positive skin test to at least one aeroallergen to indicate sensitivity, but clinical disease (allergic rhinitis) is not necessary. Exclusion Criteria: * Dermatographism or severe dermatologic condition, such as advanced eczema or psoriasis, that will not allow an adequate uninvolved area for skin testing. * Negative skin tests to penicillin G or to all aeroallergens test. * Pregnancy. * Antihistamine medications taken within one week of testing; systemic steroids, B-blockers or ACE -inhibitors taken over the previous month; omalizumab therapy at any time; those receiving or who have received immunotherapy; and those who have been desensitized to any drug within 6 months. * Allergic reaction to a B-lactam antibiotic within 1 month. * Current asthma; significant pulmonary, cardiovascular, renal, hepatobiliary or neurological diseases, or another disease process that the investigator feel would put the subject at risk of an adverse event. * Mental illness or history of drug or alcohol abuse that, in the opinion of the investigator, would interfere with the participant's ability to comply with study requirements. * Inability or unwillingness of a participant to give written informed consent.