Why Do Some People Get Sick As Soon As Vacation Starts?

Vacation is supposed to be the reward. The project is finished. The out-of-office reply is turned on. The suitcase is packed, and the stress of daily life is finally fading into the background.

Then, somehow, a sore throat appears. Or a headache. Or crushing fatigue. Or a cold that seems to arrive the moment your plane touches down.

The experience recently gained attention after a viral TikTok described something called the let-down effect. It’s the idea that some high-achieving people only become sick when they finally slow down. The video struck a nerve because many people immediately recognized the pattern from their own lives.

As it turns out, researchers have been studying a similar phenomenon for years.

A Theory That's Been Around Longer Than TikTok

The viral video may be new, but the concept isn't.

Researchers have explored a phenomenon known as leisure sickness, a term used to describe people who regularly experience headaches, fatigue, cold-like symptoms, or other health complaints during weekends, holidays, or vacations, rather than busy work periods.

The idea first gained attention through research conducted by Dutch psychologist Ad Vingerhoets. He found that some people consistently felt worse during their downtime than during their busiest stretches of work.

That doesn't mean vacations make people sick. Instead, researchers have been trying to understand why symptoms often appear when responsibilities disappear.

What Happens When We Finally Slow Down?

One possible explanation involves cortisol and stress. When we're juggling deadlines, family obligations, long commutes, and packed schedules, our bodies release hormones such as cortisol and adrenaline. These chemicals help keep us alert and focused during demanding periods.

In the short term, that stress response can be surprisingly effective. Many of us have experienced a week where we somehow powered through exhaustion, ignored a nagging headache, or pushed aside the early signs of a cold because there simply wasn't time to stop.

When the pressure finally lifts, the body shifts out of that heightened state. Researchers believe this transition may make symptoms more noticeable, particularly if an illness or period of exhaustion was already developing beneath the surface.

The Cold May Have Started Before Vacation

That's one reason experts are careful about how they describe the phenomenon. They don't believe relaxation itself causes illness.

Instead, the more likely explanation is that we're finally noticing symptoms that were already there. A virus picked up at work may have been incubating for days before the trip began. A week of poor sleep may have been slowly draining energy reserves. 

Stress may have made it easier to overlook warning signs that become harder to ignore once the schedule clears. In other words, the timing can make it seem as though vacation caused the problem when it may simply have revealed it.

Travel Can Add Its Own Challenges

Of course, vacations come with their own disruptions, too. Flights, airports, crowded tourist attractions, changes in sleep schedules, dehydration, unfamiliar foods, and exposure to new environments place additional demands on the body.

For some, the combination of travel stress and a sudden shift from constant activity to relaxation may contribute to what's often described as vacation illness.

That's why two people can take the exact same trip and have very different experiences. One returns refreshed. The other spends the first three days searching for cough drops and cold medicine.

How to Ease Into Vacation Instead of Crashing Into It

Researchers who study leisure sickness often emphasize the importance of creating a smoother transition into time off. Instead of sprinting toward vacation at full speed and stopping abruptly, some experts recommend easing into downtime, when possible.

That might mean protecting our sleep during the week before a trip, staying hydrated, avoiding the temptation to cram every last task into the final workday, and giving ourselves permission to slow down before the vacation officially begins.

None of these strategies can guarantee we won’t get sick on vacation. But, they may help us reduce some of the stress that can make the transition from work mode to relaxation mode more difficult.

Maybe Our Bodies Have Been Asking for a Break

Part of what makes the let-down effect so fascinating is how familiar it sounds. Many of us have experienced periods when we seemed capable of handling everything life threw at us, only to crash the moment the pressure eased.

Researchers are still exploring exactly why that happens. The answer is likely a combination of stress hormones, immune function, sleep, travel, and simple human biology.

Our bodies often keep score, even when we're too busy to notice. So, sometimes, a vacation doesn't create the problem. It simply gives us enough room to recognize it.

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