Two things at once: a real "let-down" pattern - a Dutch study of 1,893 people found about 3% report falling ill on weekends and holidays, clustering in the first vacation week - and plain exposure math.
The proposed mechanism: when work pressure drops abruptly, stress hormones fall and immune function reshuffles, letting incubating infections surface. The math: planes, lost sleep, new microbes, and a body run down from the pre-trip crunch. The research is thin and recall-based - real but fuzzy. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper .
What to do
Common questions
Why do I always get sick on vacation?
Two things are happening at once: a real "let-down" pattern, and plain exposure math. The pattern has a name - leisure sickness - from a Dutch study of 1,893 people that found roughly 3% reported getting sick relatively often on weekends and holidays, with infections clustering in the first week of vacation; the proposed mechanism is the stress hormone cliff: when work pressure drops abruptly, cortisol and adrenaline fall, and immune function reshuffles in a way that lets incubating infections surface. The caveats are honest: the research is thin and recall-based, so treat the 3% as a real-but-fuzzy phenomenon. The math is less fuzzy: vacations concentrate exposure - planes, airports, new time zones, lost sleep, new microbes, and a body already run down from the pre-trip crunch, which the stress-and-colds literature shows is genuinely more infection-prone. Prevention targets both: taper rather than cliff (an easy first day or two), defend sleep against jet lag, wash hands through transit days, and front-load rest. If every vacation still delivers a bug, the pre-vacation sprint is the place to intervene.