Allergic reactions after vaccination are very rare. Even if the vaccine is not clearly the cause of possible side effects, including possible allergic reactions occurring after vaccine administration, they should be reported to the appropriate authorized body. Allergic reaction occuring to other vaccine components are more likely than to the active agent, for instance to gelatine, egg protein, chicken protein, dextran, thimerosal, antimicrobials, etc. All patients with suspected allergy to vaccine components should be evaluated by an allergist. Immediate-type allergy skin testing should be performed in patients who appear to have had an allergic reaction after vaccination. This testing should help confirm that the reaction was IgE mediated and identify the responsible vaccine component. If the skin test result is negative, it is extremely unlikely that the patient will develop an allergic reaction and the patient can be vaccinated. In patients with suggestive history and positive skin tests results to vaccine components, the clinician can consider administering the alternative vaccine or the same vaccine in graded doses while observing the patient. Mild local reactions, fever, and other constitutional symptoms after vaccinations are not contraindications to subsequent doses.