Validation of Laser Doppler Flowmetry to Identify Allergic Rhinitis Patients With Pharmacogenetic Alterations in Histamine Metabolism

Inclusion Criteria: -Established diagnosis of allergic rhinitis and/or allergic conjunctivitis, and/or allergic asthma either clinically (by presence of rhinitis and/or conjunctivitis with or without associated wheezing) and/or with a positive RAST/skin test to the following allergens: trees, grass, weeds, molds, cat, dog, dust mites and/or cockroach) Exclusion Criteria: * Previous history or laboratory evidence of McCune Albright syndrome, immunodeficiency, mastocytosis, receipt of immunomodulatory treatment, chronic conditions associated with abnormalities of the integument, hepatic or renal compromise, neoplastic disease, movement or neurologic disorders and uncontrolled ADHD * Active atopic dermatitis at the site of the skin prick test or site where histamine iontophoresis will be performed, i.e. active atopic dermatitis on anterior forearms * History of anaphylaxis or anaphylactic like episode * Evidence of pregnancy (by urinary hCG) or lactation * Use of drugs (within a specified time period) of agents capable of altering the response to histamine provocation (e.g., antihistamines, systemic corticosteroids, tricyclic antidepressants) * Presence of any condition that, in the opinion of the investigator, would produce difficulty with adherence to study procedures.