Since December 2020, in various countries of the world, many cases of severe allergic reactions after administration of PfizerBioNTech COVID-19 vaccine, were reported. A great concern has arisen among the doctors who administer the vaccine and the allergic patients who undergo vaccinations. In Italy guidelines were published in order to stratify the risk in the allergic population. In mRNA vaccines, the component currently suspected of causing allergic reactions is the polyethylene glycol excipient (PEG or macrogol). In patients who have shown an immediate allergic reaction to vaccine and who are negative to skin tests for PEG, desensitization with the same vaccine is proposed. In this paper we describe two cases of asthma after the first COVID vaccine administration in which desensitization has failed.

Background/Objectives: Drug hypersensitivity reactions (DHRs) are an important cause of morbidity in hospitalized patients, but their epidemiology and management in the inpatient setting are not well defined. Mislabeling of drug allergies may lead to inappropriate treatment and reduced antimicrobial stewardship. This study aimed to characterize the clinical profile, diagnostics, and management of inpatients referred for suspected drug allergy in a tertiary care hospital. Methods: We retrospectively reviewed all adult inpatients (≥18 years) at Luigi Sacco Hospital (Milan, Italy) who received allergology consultation between 1 June 2022 and 31 May 2025. Data on demographics, reaction type, culprit drugs, investigations, and management were collected. Immediate reaction severity was graded using the United States Drug Allergy Registry (USDAR) scale; delayed reactions were classified as severe cutaneous adverse reactions (SCARs) or non-SCARs. Logistic regression identified predictors of severity. Results: Among 35,438 admissions, 334 patients (0.9%) were evaluated; median age was 65 years, 51.2% were female, 67.4% had atopic comorbidities, and 55.1% reported prior drug allergy. Immediate reactions occurred in 49.1%, delayed in 43.7%. Cutaneous involvement was present in 86.8%, anaphylaxis in 6.6%, and SCARs in 3.9%. Antibiotics—particularly β-lactams—were most often implicated. In multivariate analysis, antibiotic exposure and older age were linked to more severe immediate reactions, while the absence of atopy predicted SCARs. Desensitization was successfully performed in 16.2% of patients. Conclusions: DHRs in inpatients are frequent and often involve high-risk drugs. Structured inpatient allergology services and an “allergy stewardship” approach may reduce DHR-related risks, support optimal therapy, and improve antimicrobial use strategies in tertiary care settings.

Alpha-gal syndrome (AGS) is caused by the intake of products containing alpha-gal (galactose alpha-1,3-galactose) like mammalian meat. Over the last decade, scientific literature about AGS has been increasing, but the true burden of cases is still unknown [1, 2]. In the USA (University of Virginia Allergy Clinic), the number of confirmed cases of AGS was 24 in 2009 [3] and increased to 34,000 in the entire USA by 2019 [4]. As shown in surveys, in Italy AGS is present throughout the country [5]. The literature suggests that a previous tick bite can cause AGS, but in our case it was not possible to demonstrate this association as the patient did not recall any tick bite, even in childhood. After eating red meat, a 56 -year -old male patient had developed symptoms such as generalized urticaria, diarrhea, and faintness, requiring admission to the Emergency Department. The diagnosis was verified using blood CAPFEIA test and prick -to -prick test. After completing the diagnostic process, we provided the patient with emergency therapy, and autoinjectable adrenaline was prescribed. Despite the diagnosis, the patient ate red meat once again which resulted in severe urticaria 2 hours after the meal, requiring a second visit to the Emergency Room. Now the patient is under follow-up at our Department of Allergy and Clinical Immunology.

Scombroid syndrome is a frequent cause of fish poisoning and typically presents with mild, self-limiting symptoms. Severe anaphylaxis-like reactions are uncommon, and a biphasic clinical course has not previously been reported. We describe the case of a 19-year-old woman who developed flushing, headache, generalized urticaria, facial edema, dyspnea, and hypotension approximately 30 minutes after ingesting raw amberjack tartare. Emergency treatment with adrenaline, antihistamines, corticosteroids, and intravenous fluids led to initial clinical improvement; however, three hours later, she experienced a recurrence of cutaneous, respiratory, and gastrointestinal symptoms, consistent with a biphasic reaction. The patient subsequently developed chest pain associated with transient electrocardiographic changes and mild troponin elevation, prompting further evaluation for suspected Kounis syndrome. Allergy assessment, including specific IgE testing and skin-prick testing with fresh fish, was negative, supporting a toxic rather than IgE-mediated mechanism. This case expands the clinical spectrum of scombroid syndrome by documenting a biphasic anaphylaxis-like presentation and underscores the importance of considering histamine fish poisoning in the differential diagnosis of severe food-related reactions. Careful evaluation is essential to prevent misdiagnosis and unnecessary long-term dietary restrictions.