Why Many Professionals Get Sick on the First Days of Holiday

va·ca·tion | noun | an extended period of leisure and recreation, especially one spent away from home or in travelling.

Sounds lovely. Doesn’t mention the part where a meaningful percentage of the working population spends the first 48 hours of it in bed with a sore throat, a migraine, or a stomach that has filed a formal complaint. Nobody puts that bit in the brochure.

Meet the Collector

Somewhere in your physiology there is a very patient guy whose entire job is keeping tabs on what you owe. Let’s call him the Collector. All year, while you’re pulling long weeks, skipping lunch, running on caffeine and closing out the quarter, he is quietly opening a file on you. He notices the sleep debt. He notices the immune system running on a skeleton crew. He notices every corner you cut just to keep functioning. He writes it all down.

But here is the thing about the Collector. He does not actually show up while you are busy. He cannot. While your stress system is fully engaged, your body is, biologically speaking, refusing his calls. It is dealing with what it perceives as more urgent business.

This is well established physiology, not a metaphor stretched past its limits. Acute stress genuinely does suppress immune and inflammatory activity in the short term, as part of the body’s normal response to a demanding situation (Segerstrom & Miller, 2004). Useful if you are being chased by something. Also useful, it turns out, if you are being chased by a board deck due Thursday. Either way, the Collector gets told to wait outside.

Why He Always Picks the First Day of Holiday

The trouble starts the moment you actually stop. The second your stress system realises the emergency, real or perceived, has passed, it starts standing down. And that is exactly the moment the Collector finally gets let in the building.

A small 2002 study of Dutch professionals gave this pattern an actual name: leisure sickness, falling ill specifically during weekends or holidays rather than during working periods. About 3% of a representative sample recognised the pattern, and it showed up more strongly among people with heavy workloads and difficulty switching off than among people who simply relaxed (Vingerhoets, Van Huijgevoort, & Van Heck, 2002). The study was small and its own authors called for more research, so treat it as a strong hint rather than a verdict. But the shape of it is hard to ignore. Symptoms were not showing up because people finally rested. They were showing up because people finally stopped holding the Collector off.

The Invoice Was Always Coming

Here is the useful way to think about this. Every skipped recovery, every all-nighter before a launch, every holiday you spent still half-logged into your inbox, went straight onto the Collector’s ledger. None of it vanished just because you did not feel it at the time. Researcher Bruce McEwen described this accumulation as allostatic load, the wear and tear that builds up in a body that keeps mobilising for demand without adequate time to recover (McEwen, 1998). The Collector does not forgive the balance. He just waits for a moment when you are not actively defending yourself.

And the first days of a holiday are, unfortunately, his favourite collection window. You have stopped bracing. Your cortisol is dropping. Your guard, physiologically speaking, is finally down. From his perspective, this is not bad timing. It is the only appointment slot you ever actually gave him.

He Is Not Always This Aggressive

To be fair to the Collector, he does not always show up wielding a sore throat and a migraine. Sometimes he is reasonable about it. If you have been paying down the balance regularly, taking real breaks, actually detaching rather than just being physically present somewhere sunny, he tends to collect gently, or barely notice you at all.

A recent meta-analysis of vacation research found that time off genuinely can improve wellbeing, but the benefit depends heavily on two things: whether people psychologically detach from work, and whether they stay physically active during the break (Grant, Buchanan, & Shockley, 2025). Psychological detachment specifically, actually switching off mentally and not just leaving the building, has for years been one of the clearest predictors of whether time off actually restores anyone (Sonnentag & Fritz, 2007).

Which means a person can be sitting on a beach in Portugal while still fully logged into the office in every way that matters to the Collector. Physically absent. Mentally still very much on the clock. From his ledger, that barely counts as a payment.

Why This Should Worry Your Employer, Not Just You

Most companies only ever meet the Collector once he has already sent someone home sick, or once a normally reliable person quietly turns brittle and nobody can say exactly why. By then he has been running a tab for months and nobody thought to check the balance.

Worth asking honestly, if you are the one setting the pace for a team. Does your final week before a break look suspiciously like a sprint? Do people actually detach when they are off, or are they just relocating the same workload somewhere with better weather? Is recovery something your culture treats as a continuous cost of doing business, or as an annual emergency that gets dealt with once a year, usually badly, usually in the first 48 hours of somebody’s holiday?

These are not HR questions dressed up to sound important. They are closer to asking whether anyone is actually reconciling the books.

The Bottom Line

The first days of a holiday probably do not make people sick. They just happen to be the first moment all year when nobody is holding the Collector off any longer.

Which reframes the whole thing rather usefully. Getting ill the moment you finally stop was never really bad luck. It was closer to a scheduled visit from someone who has been trying to reach you for months, and who finally caught you home.

The actual fix was never harder holidays. It is paying down the balance regularly enough that he never needs to show up at all.

This article is part of our ongoing exploration of Sustainable Performance through the lens of human physiology.

Author: Giorgio Bruins

Date: 04/08/2026

Sources

Vingerhoets, A. J. J. M., Van Huijgevoort, M., & Van Heck, G. L. (2002). Leisure sickness: A pilot study on its prevalence, phenomenology, and background. Psychotherapy and Psychosomatics, 71(6), 311–317.

Segerstrom, S. C., & Miller, G. E. (2004). Psychological stress and the human immune system: A meta-analytic study of 30 years of inquiry. Psychological Bulletin, 130(4), 601–630.

McEwen, B. S. (1998). Protective and damaging effects of stress mediators. New England Journal of Medicine, 338(3), 171–179.

Grant, R. S., Buchanan, B. E., & Shockley, K. M. (2025). I need a vacation: A meta-analysis of vacation and employee well-being. Journal of Applied Psychology, 110(7), 887–905.

Sonnentag, S., & Fritz, C. (2007). The Recovery Experience Questionnaire: Development and validation of a measure for assessing recuperation and unwinding from work. Journal of Occupational Health Psychology, 12(3), 204–221.