Cold plunging involves short-term submersion in cold water and has gained popularity for its potential health benefits. For a healthy person, this deliberate cold shock can be a beneficial form of conditioning. However, when the body is actively fighting an infection, adding this extreme temperature stress requires careful consideration of the risks. The body’s systems are already taxed during illness, and introducing a powerful physiological trigger like a cold plunge may be harmful.
How Cold Exposure Affects the Immune System
Acute cold exposure activates the sympathetic nervous system, leading to a significant increase in circulating norepinephrine. This surge helps to mobilize immune cells throughout the body. Studies suggest that cold exposure can induce a temporary increase in white blood cell counts (leukocytosis), specifically raising the number of natural killer cells and granulocytes in the bloodstream.
The rapid circulation of white blood cells is thought to be an immunostimulating effect, which proponents cite for better long-term immunity. This temporary redistribution of immune cells is a stress response that, for a healthy person, could be a form of beneficial stress (hormesis). However, these observed immune responses are based on studies of healthy individuals, and the effect on a body already battling a pathogen is not clearly established.
Physiological Stress During Illness
Illness, especially when accompanied by fever, places the body in a high-stress, metabolically demanding state. Introducing a cold plunge adds an immediate and intense physical stressor that can be counterproductive to recovery. The sudden immersion triggers powerful vasoconstriction, where blood vessels narrow sharply to conserve core heat.
This redirection of blood flow places a significant burden on the cardiovascular system. The heart must work harder to pump blood against increased resistance, leading to an elevated heart rate and blood pressure. This strain is ill-advised when the body is already working overtime to fight infection.
Cold immersion can interfere with the body’s natural thermoregulatory process, which uses fever to fight infection. When vasoconstriction occurs, it can inadvertently trap heat in the core, potentially worsening a fever. The body’s energy is then redirected toward maintaining core temperature, pulling metabolic resources away from viral or bacterial defense.
When to Absolutely Avoid Cold Plunges
Certain symptoms and conditions serve as absolute contraindications, meaning cold plunging should be avoided entirely to prevent complications. If a person has a fever, they should not attempt a cold plunge, as it can confuse temperature regulation and potentially exacerbate the fever. Severe fatigue or profound weakness, which indicate the body is highly resource-depleted, are also clear signals to avoid the practice.
Any respiratory distress, such as chest congestion or difficulty breathing, is another reason to abstain. Cold water immersion triggers an immediate gasp reflex and hyperventilation, which can intensify discomfort and create unnecessary risk when airways are compromised. Individuals with pre-existing cardiovascular conditions should avoid cold plunges entirely when sick due to the added strain on the heart and the risk of severe blood pressure fluctuations.