Vaccines constitute the most effective medications in public health as they control and prevent the spread of infectious diseases and reduce mortality. Similar to other medications, allergic reactions can occur during vaccination.While most reactions are neither frequent nor serious, anaphylactic reactions are potentially life-threatening allergic reactionsthat are encountered rarely, but can cause serious complications.The allergic responses caused by vaccines can stem fromactivation of mast cells via Fcε receptor-1 type I reaction, mediated by the interaction between immunoglobulin E (IgE) antibodies against a particular vaccine, and occur within minutes or up to four hours. The type IV allergic reactions initiate 48 h after vaccination and demonstrate their peak between 72 and 96 h. Non-IgE-mediated mast cell degranulation via activation of the complement system and via activation of the Mas-related G protein-coupled receptor X2 can also induce allergic reactions. Reactions are more often caused by inert substances, called excipients, which are added to vaccines to improve stability and absorption, increase solubility, influence palatability, or create a distinctive appearance, and not by the active vaccine itself. Polyethylene glycol, also known as macrogol, in the currently available Pfizer-BioNTech and Moderna COVID-19 mRNA vaccines, and polysorbate 80, also known as Tween 80, in AstraZeneca and Johnson & Johnson COVID-19 vaccines, are excipients mostly incriminated for allergic reactions. This review will summarize the current state of knowledge of immediate and delayed allergic reactions in the currently available vaccines against COVID-19, together with the general and specific therapeutic considerations. These considerations include:The incidence of allergic reactions and deaths under investigation with the available vaccines, application of vaccination in patients with mast cell disease, patients who developed an allergy during the first dose, vasovagal symptoms masquerading as allergic reactions, the COVID-19 vaccination in pregnancy, deaths associated with COVID-19 vaccination, and questions arising in managing of this current ordeal.Careful vaccine-safety surveillance over time, in conjunction with the elucidation of mechanisms of adverse events across different COVID-19 vaccine platforms, will contribute to the development of a safe vaccine strategy.Allergists’ expertise in proper diagnosis and treatment of allergic reactions is vital for thescreening of high-risk individuals.

There is an emerging need for application of sensitive non-invasive and easily measured biomarkers of early intestinal injury (e.g., citrulline, intestinal fatty acid protein, and zonulin) in our everyday clinical practice, guiding the early pharmacological intervention in critically ill patients to restore or prevent intestinal injury and improve their outcomes.

This study demonstrates for the first time that human liver cirrhosis induces significant alterations in enterocytes' TJs. These changes might represent an important cellular mechanism for intestinal barrier dysfunction and hyperpermeability in patients with liver cirrhosis.

Tight junctions �T�s�� are structures bet�een cells �here �T�s�� are structures bet�een cells �here are structures bet�een cells �here cells appear in the closest possible contact. They are responsible for sealing compartments �hen epithelial sheets are generated. They regulate the permeability of ions, �macro�� molecules and cells via the paracellular path�ay. Their structure at the electron microscopic level has been �ell kno�n since the 1970s; ho�ever, only recently has their macromolecular composition been revealed. This revie� first examines the major macromolecular components of the T�s �occludin, claudins, junctional adhesion molecule and tricellulin�� and then the associated macromolecules at the intracellular plaque [zonula occludens �ZO��-1, ZO-2, ZO-3, AF-6, cingulin, 7H6]. Emphasis is given to their interactions in order to begin to understand the mode of assembly

This study shows that experimental obstructive jaundice induces intestinal oxidative stress, which may be a key factor contributing to intestinal injury and leading to endotoxin translocation.