Urtikaria nach SARS-CoV-2-Impfung

Background: Infections are considered the most common known trigger of acute urticaria. Vaccinations can mimic infections and are also able to trigger urticaria. Methods: This paper describes four exemplary patients with urticaria after SARSCoV-2 vaccination and discusses the occurrence of this adverse event with recent findings from the literature. Results: After SARS-CoV-2 vaccination, both acute (case 1) and chronic spontaneous urticaria (CSU) may occur for the first time (case 2) but a stable well-adjusted CSU may also worsen (case 3) or a pre-existing CSU may recur (case 4). The underlying pathomechanisms are not fully elucidated but activation of the immune system by vaccination seems plausible, similar to infection-triggered urticaria. Subsequent vaccinations are recommended even in the presence of a positive history of urticaria after SARS-CoV-2 vaccination and is often well tolerated; prophylactic administration of antihistamines should be considered. Allergy to vaccine components such as polyethylene glycol (PEG), which can lead to anaphylaxis, is comparatively rare. In cases of urticaria after SARS-CoV-2 vaccination, an accurate history allows risk assessment and provides the indication for further allergy diagnostic workup. Conclusion: Various forms of urticaria are a relatively common cutaneous side effect of SARS-CoV-2 vaccination in cases of pre-existing predisposition. They are not a contraindication to further vaccination. There is no need for further allergy diagnosis in the majority of cases.