A common link among allergic diseases remains the many allergens that can provoke symptoms. The National Institutes of Health Guidelines for the Diagnosis and Management of Asthma and Guidelines for the Diagnosis and Management of Food Allergy support the use of in vivo (skin prick) or in vitro (blood) specific immunoglobulin E (IgE) testing, along with a detailed clinical history and physical examination, to document an allergy diagnosis. The initial responsibility of diagnosing allergic diseases falls principally on primary care providers, for whom skin prick testing is impractical. Access to in vitro testing provides a valuable diagnostic tool, in conjunction with patient history, for comprehensive allergy and asthma management, which can result in significant clinical and economic benefits and improved patient outcomes. Identification of specific allergens in patients enhances management through education, targeted allergen avoidance, pharmacotherapy, and immunotherapy. The utilization of specific IgE in vitro allergy testing may also drive efficient and effective utilization of healthcare resources. Testing can facilitate a close collaboration between the primary care provider and the allergy specialist, who is experienced in interpreting allergy tests and correlating them with clinical history, conducting food and drug challenges, educating about environmental controls, and managing chronic or recurrent conditions where allergy is not easily recognized. As healthcare reimbursement moves from fee-for-service to fee-for-outcomes, cooperative, comprehensive, and outcome-based patient management will gain in importance.