Why You Get Sick During Time Off: The Cortisol Dip Effect Explained

You power through weeks (or months) of deadlines, late nights, travel, and stress. You finally take time off. And instead of feeling refreshed… you get sick.

If you’ve ever come down with a cold on the first day of vacation or gotten knocked out during the holidays, you’re not imagining things and you’re definitely not alone.

This frustrating phenomenon is so common that researchers have a name for it: the “let-down effect.” And once you understand what’s happening in your body, especially at the level of stress hormones and neurotransmitters, it starts to make a lot more sense.

The good news? With the right nutrients and habits, you can support your body before and after time off so rest actually feels restorative, not like a crash.

Why Getting Sick During Time Off Is So Common

Research has consistently shown that people are more likely to develop symptoms of illness after periods of prolonged stress, rather than during the stress itself.

One landmark study published in the New England Journal of Medicine found that individuals exposed to chronic stress were significantly more likely to develop cold symptoms after the stressful period ended — even when exposed to the same virus as others who stayed healthy.

In other words:
Stress doesn’t always make you sick immediately. It often delays the symptoms.

This is the foundation of the cortisol dip effect.

The Cortisol Dip Effect: Stress Is Propping You Up (Until It Isn’t)

Cortisol gets a bad reputation, but it’s not inherently harmful. It’s a survival hormone designed to help you power through short-term challenges.

During prolonged stress:

• Cortisol stays elevated

• Inflammation is temporarily suppressed

• Immune symptoms are muted

• You “push through” fatigue, poor sleep, and nutrient depletion

This is why many people don’t get sick during their busiest or most stressful periods.

But when the stress suddenly stops — like when a vacation begins or the holidays finally slow down — cortisol levels drop. And when cortisol drops quickly, immune activity rebounds — and that’s often when symptoms like fatigue, congestion, or a sore throat appear.

Why Vacations and Holidays Are the Perfect Storm

Time off isn’t always as restful as it looks on paper.

Travel adds:

• Sleep disruption

• Time zone shifts

• Dehydration

• Exposure to new pathogens

Holiday habits often include:

• Alcohol

• Sugar-heavy meals

• Less protein and micronutrients

• Later nights and inconsistent routines

Sleep deprivation alone has been shown to significantly reduce immune function and increase susceptibility to illness.

Add that on top of a cortisol drop and depleted nutrient reserves, and it’s no surprise your body waves the white flag.

The Fix Isn’t “More Immune Boosting” — It’s Replenishment

Most people approach this problem backward. They try to “boost” the immune system after they get sick.

But the real strategy is supporting stress recovery and neurotransmitter balance with targeted nutrients — so your immune system doesn’t crash when cortisol drops.

Best Nutrients for Stress Recovery & Immune Function

These are the best science-backed nutrients to support your immune system so that you feel good during and after your time off.

Magnesium

Magnesium is one of the most important minerals for both stress recovery and immune health. It helps immune cells do their job, supports healthy inflammation levels, and plays a role in activating vitamin D — a nutrient essential for immune function.

Chronic stress, poor sleep, and alcohol can all drain magnesium levels, which may make it harder for the body to fight off illness when stress finally lets up. Supporting magnesium intake with Mood Magnesium can help the immune system respond more smoothly during times of stress and recovery*, like vacations or holidays.

B Vitamins

B vitamins play a critical role in energy production, brain chemistry, and immune health. They’re involved in the creation of neurotransmitters like serotonin and dopamine, as well as the production of immune cells and antibodies.

During periods of chronic stress, the body burns through B vitamins more quickly, which can leave you feeling run-down and more vulnerable to getting sick once you slow down.

Supporting adequate B vitamin intake with methylated Mood B Complete vitamins can help the body adapt to stress and maintain a resilient immune response during recovery periods like vacations or time off.*

Omega 3s

Omega-3 fatty acids, especially EPA and DHA, are essential for regulating inflammation and supporting immune signaling. Omega-3s help keep immune responses balanced — strong enough to defend against illness without becoming overly inflammatory. 

Research shows omega-3s also support brain health and stress resilience, which matters because chronic stress and inflammation can weaken immune defenses over time. Maintaining healthy omega-3 levels with Mood Omegas can support both immune health and recovery after prolonged stress.*

Probiotics

A large portion of the immune system is located in the gut, making gut health a key factor in immune resilience. Stress, travel, poor sleep, and changes in routine can disrupt the gut microbiome, which may affect how well the immune system responds.

Probiotics like Mood Biotics can help support a healthy balance of gut bacteria, strengthen the gut barrier, and support communication between the gut and immune system.* Supporting gut health is especially important during travel, holidays, and other times when stress and routine changes are high.

GABA and L-Theanine

GABA and L-theanine support relaxation and nervous system balance, which play an indirect but important role in immune health. Chronic stress keeps the body in a constant “fight-or-flight” state, which can suppress immune function over time.

L-theanine has been shown to promote relaxation and reduce stress responses without causing drowsiness, while GABA supports calm signaling in the brain. Supporting nervous system regulation with Mood Chews can help the body transition more smoothly from stress to rest — reducing the likelihood of feeling run-down or getting sick when you finally slow down.*

TL;DR

Getting sick during time off isn’t bad luck — it’s a common response to coming out of prolonged stress. While you’re under pressure, stress hormones like cortisol help you push through by keeping inflammation and immune signals quieter. When that stress finally eases, cortisol levels drop and the immune system becomes more active, which is often when fatigue, congestion, or cold symptoms show up.

Chronic stress also depletes key nutrients that support the nervous system and immune function. Replenishing magnesium, B vitamins, omega-3s, probiotics, and calming amino acids can help the body transition more smoothly from stress to rest, so time off actually feels restorative instead of leaving you run-down.

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*These statements have not been evaluated by the Food and Drug Administration. These products are not intended to treat any medical condition. Please consult with your healthcare professional before adding new supplements to your routine.

FAQs

Why do I always get sick during the holidays?

Because stress hormones suppress symptoms — and when cortisol drops, inflammation and immune signaling rebound.

Why do I get sick during vacation?

Vacation removes stress hormones while adding sleep disruption, travel strain, and pathogen exposure.

Can traveling affect the immune system?

Yes. Sleep loss, dehydration, circadian disruption, and stress all reduce immune defenses.

How do I prevent getting sick on vacation?

Support stress recovery before time off with magnesium, B vitamins, omega-3s, gut support, sleep, and hydration.

What supplements help boost the immune system?

Rather than overstimulation, the most effective strategy is nervous system regulation and nutrient repletion — including magnesium, B vitamins, omega-3s, probiotics, and calming amino acids.

References

1. https://www.nejm.org/doi/full/10.1056/NEJM199108293250903
2. https://pmc.ncbi.nlm.nih.gov/articles/PMC8602722/
3. https://www.sciencedirect.com/science/article/abs/pii/S0946672X25000173
4. https://pmc.ncbi.nlm.nih.gov/articles/PMC6693398/
5. https://www.sciencedirect.com/science/article/abs/pii/S0378512216302997
6. https://youcanpym.com/blogs/learn/what-supplements-affect-serotonin-levels?_pos=2&_psq=serotonin&_ss=e&_v=1.0
7. https://pmc.ncbi.nlm.nih.gov/articles/PMC9190671/
8. https://pmc.ncbi.nlm.nih.gov/articles/PMC8001875/
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC3539293/
10. https://pmc.ncbi.nlm.nih.gov/articles/PMC6366437/
11. https://pmc.ncbi.nlm.nih.gov/articles/PMC7527439/