Chronic urticaria; Full body rash/ the rash was itchy, red, hot, and the rash has welts; Full body rash/ the rash was itchy, red, hot, and the rash has welts; Full body rash/ the rash was itchy, red, hot, and the rash has welts; This spontaneous case was received on 03-Jan-2023 from other non-healthcare professional (consumer) via Communications (reference number: SEQW23-00017) and concerned a 24-year-old, female patient.   The patient's medical history was not reported. The patient's concomitant medications included unspecified contraceptive pill, used for unreported indication. The patient did not have allergies to anything.  On 01-Oct-2022, the patient was vaccinated with Flucelvax Quadrivalent (influenza vaccine inact sag 4v; dose: 0.5 ml, route of administration, anatomical location: not reported) for active immunization for the prevention of influenza disease caused by influenza virus subtypes A and B contained in the vaccine. The batch number reported was 942378 and expiration date was 03-Jun-2023.   On an unspecified date in Oct-2022 (discrepantly reported as '01-Oct-2023'), about eight to ten hours after receiving Flucelvax Quadrivalent, the patient developed a full body rash. The rash was itchy, red, hot, and the rash had welts. The patient thought it was more like hives than an actual rash. The patient developed chronic urticaria and it was pretty debilitating. Ever since the event at hand, the patient had been taking Zyrtec (cetirizine hydrochloride), every two days.   On 02-Oct-2022, the patient went to the Hospital Emergency Room (ER) as she thought her throat was going to close and would have anaphylaxis. The patient was reportedly given unspecified steroids, Benadryl (diphenhydramine hydrochloride) and pepsin. The patient was discharged the same day.  At the time of initial reporting, the patient was recovering from the events. The symptoms were still coming but were less severe. The patient was about to see an allergologist the same week, and to report any new information.  The reporter assessed the events to be related to Flucelvax Quadrivalent. The patient had never experienced a reaction like the described and claimed that it must have been a consequence of the vaccine as there were no other triggers. The patient stated that she developed a chronic urticaria from the immunization.  All events were assessed as serious due to the seriousness criterion of medical significance.  Company comment: A 24-year-old, female patient was vaccinated with the suspect product Flucelvax Quadrivalent. As reported about eight to ten hours after vaccination the patient developed a full body rash that was pruritic, red, hot, and the rash had welts. The patient thought it was more like hives than an actual rash. As reported, the patient developed chronic urticaria. Information regarding the underlying medical history and related diagnostic findings has not been provided. Causality for the events chronic urticaria, and warm pruritic erythematous rash is assessed as possibly related based on plausible temporal relationship.; Reporter's Comments: The patient had never experienced a reaction like the described and claimed that it must have been a consequence of the vaccine as there were no other triggers. The patient stated that she developed a chronic urticaria from the immunization; Sender's Comments: A 24-year-old, female patient was vaccinated with the suspect product Flucelvax Quadrivalent. As reported about eight to ten hours after vaccination the patient developed a full body rash that was pruritic, red, hot, and the rash had welts. The patient thought it was more like hives than an actual rash. As reported, the patient developed chronic urticaria. Information regarding the underlying medical history and related diagnostic findings has not been provided. Causality for the events chronic urticaria, and warm pruritic erythematous rash is assessed as possibly related based on plausible temporal relationship.