An adverse drug reaction relates to an undesired response to administration of a drug. Type A reactions are common and are predictable to administration, dose response, or interaction with other medications. Type B reactions are uncommon with occurrences that are not predictable. Appropriate diagnosis, classification, and entry into the chart are important to avoid future problems. The diagnosis is made with careful history, physical examination, and possibly allergy testing. It is recommended that help from allergy immunology specialists should be sought where necessary and that routine prescription of Epi pen should be given to patients with multiple allergy syndromes.