Allergy and hypersensitivity diseases in space: physiological changes, clinical aspects, and mechanisms with countermeasures

Allergy and hypersensitivity diseases are important topics worldwide. The development of allergies in humans has become increasingly common and is expected to increase in the next future, the incidence is expected to reach 50 % of the worldwide adult population. The space is not left out in this phenomenon. Having allergy requires further care, considering that astronauts spend time far away from home, working with widely diverse materials for science experiments and repairing stations. A history of atopy is checked during the selection process and can request further investigation to make sure the crew and mission will not be impacted. It is not itself a disqualifying criterion: it has to be balanced with all other parameters. Space is a very extreme environment for the body which increase the risk to develop allergy or hypersensitivity. This article focuses on the specificity of space by reviewing the very challenging and extreme environment of space: microgravity, radiation, isolation and other specificity of the International Space Station. The space-related clinical diseases, including allergies, and the mechanisms and countermeasures used in space to avoid major clinical events were also reviewed. One of the major consequences of space in the topic of allergy is the change in the immune system. If the immune system is altered, the capacity for recovery is impacted, and more critical infections can be expected in space. Further studies are needed to ensure the safety of next interplanetary travel to space. In this review new countermeasures are mentioned, they seem promising but need further research on human bodies to ensure safe travel to space.