It’s pretty common to hear during winter “bundle up or you’ll get sick”. 

There’s some truth to that. Respiratory viruses like the flu or the common cold are more frequent in winter.

But, what if we told you that cold exposure might have the opposite effect? Research suggests that cold exposure could strengthen the immune system and protect the body against colds, the flu, and other illnesses.

What is the Immune System?

The immune system is the body’s natural defense against disease.

It’s a network of cells, organs, and tissues — such as white blood cells, the spleen, bone marrow, and lymph nodes — that work together to identify and eliminate viruses, bacteria, and fungi.

Cold Exposure and the Immune System: How Are They Connected?

One of the first clues about the immune benefits of cold exposure came from studies on winter swimmers. In Nordic countries, it’s common to see people immersing themselves in water close to 1°C.

In one study, researchers in Helsinki recruited 20 healthy adults, 12 of whom were regular winter swimmers and 8 who were not. All participants had two blood samples taken: one at rest and another after immersing themselves for one minute in an ice-cold lake.

What did winter swimmers show?

• A higher number of white blood cells than those who did not expose themselves to the cold.

• A more intense immune response compared to people unaccustomed to the cold.

Why Does Cold Activate the Immune System?

The key lies in the stress paradox: low, controlled doses of stress can produce beneficial adaptive responses.

Cold-plunging is precisely that — a controlled stressor. Extreme cold (stress) triggers the release of adrenaline, dopamine, and endorphins (positive outcome), strengthening both body and mind.

This also makes sense from an evolutionary perspective. Our ancestors faced extreme challenges: harsh climates, injuries, infections. Those who experienced increased immune activity were more likely to survive in those conditions.

So, it makes sense that our immune system evolved to mobilize in response to an acute stressor. Cold-exposure simulates those conditions, helping keep that ancestral mechanism active.

Benefits of Cold-Plunging for the Immune System

Increase in White Blood Cells

Cold-plunging increases the number of white blood cells and raises anti-inflammatory chemicals. Both are essential for fighting illness and infection.

Boost in Blood Circulation

During an ice-bath session, blood vessels constrict to send blood to the core and protect vital organs. When you exit the water, oxygenated blood flows back to the extremities.

In this process, the heart pumps harder and blood moves faster, delivering more oxygen- and nutrient-rich blood throughout the body. This boosts cell growth, which has a positive effect on the immune system.

Toxin Elimination

Increased blood flow also helps eliminate toxins, improving overall health.

Lower Cortisol Levels

Cold-plunging helps release large amounts of endorphins, which lower cortisol (the stress hormone), indirectly supporting the immune system.

Enhanced Cellular Function

When cells operate at their optimal level, every system in the body functions better. Cold-plunging enhances cell growth and function — essential for a strong, efficient immune system.

An important note: if you have the flu or have any type of sickness, don't cold-plunge. Your body is already stressed, it doesn't need to be overtaxed. Wait until you're fully recovered before cold-plunging again.

Conclusion

Don't let the fear of getting sick or "catching the flu" stop you from trying cold-plunging. 

Embrace the cold with our Ice Baths Pro: 24/7 cold therapy without having to carry around kilos and kilos of ice. Learn more on the Homepage.

(*) Alfa Humans is designed to support a healthy lifestyle, not to diagnose, cure, or prevent diseases or medical conditions. Our tubs are not medical devices. Consult your doctor before beginning any deliberate cold-exposure practice.