Currently available vaccines are safe but, potentially, any vaccine can cause an allergic reaction and albeit very rare, anaphylaxis can occur. Although its rarity, the precise diagnostic management of a suspected anaphylaxis post-vaccination is of paramount importance due to the risk of a potential serious reactions after re-exposure, while, a misdiagnosis might lead to an increase in the number of children that interrupt vaccinations resulting in an unjustifiably individual and collective risk of loss of protection against immune preventable diseases. Especially, in the light that most cases of suspected allergy to a vaccine are not effectively confirmed in up to 85% of the patients referred for an allergy evaluation and patients can continue vaccination with the same formulation and tolerance of the booster doses The patient assessment has to be done by an allergist or an immunologist expert in the vaccine field to select subjects at risk of allergic reactions and to perform the correct procedures for vaccine hypersensitivity diagnosis and management, in order to guarantee safe immunization practices. Aim of this review is to provide a practical and safe management in the clinical settings of the allergic patient which have to undergo immunization practices, both to manage children with a suspected allergic reaction to a vaccine both children with history of allergy to a vaccine component.