Using an outdoor hot tub when the air temperature is near freezing often raises a common concern: the fear of catching a cold or becoming ill from the drastic temperature change. While the temperature itself is not the source of illness, the unique environment of a hot tub, especially in winter, introduces risks ranging from physiological stress to exposure to unseen pathogens. Understanding the true mechanisms of infection and heat loss is important for safely enjoying a warm soak during cold weather.
The Truth About Temperature and Viral Illness
The idea that simply being cold or experiencing a temperature shift causes a viral infection is a long-standing misconception. Illnesses like the common cold and influenza are caused solely by specific viruses, which must be present and transmitted. Exposure to cold air cannot create a virus where none exists.
Temperature exposure can, however, alter the body’s ability to defend itself. Studies show that a drop in the temperature inside the nasal cavity can reduce the immune response by nearly half.
This temporary weakening makes the respiratory tract more susceptible if a virus is already inhaled. Additionally, cold, dry air conditions can increase the survival rate of certain viruses in the environment, making transmission easier.
Waterborne Infections: The Real Danger in Hot Tubs
The true health risks associated with hot tub use stem not from the cold air, but from the water itself if it is not maintained correctly. Hot tubs are warm, aerated environments that provide ideal conditions for bacterial growth. High temperatures (100°F to 104°F) cause disinfectants like chlorine to break down quickly, leaving the water vulnerable to contamination.
One common issue is “hot tub rash,” or Pseudomonas folliculitis, caused by the bacterium Pseudomonas aeruginosa. This infection causes an itchy, bumpy rash, often severe in areas covered by a wet swimsuit, which holds the contaminated water against the skin.
A far more serious threat is Legionella bacteria, which causes Legionnaires’ disease, a severe form of pneumonia. Legionella thrives in warm water and is dangerous because the jets and aeration create a fine mist or aerosol. When these contaminated water droplets are inhaled, the bacteria are deposited directly into the lungs, causing infection. The visible steam rising in cold air is a reminder of this aerosolization process, which is the primary route of transmission for this respiratory illness. The risk of these waterborne diseases is present year-round but is exacerbated by inadequate maintenance.
Managing Physiological Stress from Extreme Temperature Shifts
Moving rapidly from the heat of the tub into freezing outdoor air places immediate stress on the cardiovascular system. The body’s response to heat is vasodilation, where blood vessels widen to release heat. Upon exiting, the body quickly initiates vasoconstriction, where peripheral blood vessels rapidly narrow to conserve core heat.
This sudden change in vascular diameter can cause a temporary spike in blood pressure as the heart works harder to pump blood through the constricted vessels. Individuals with pre-existing heart conditions should be cautious, as this rapid change can increase the risk of a cardiac event.
Remaining wet in the cold air also leads to rapid evaporative heat loss. This process quickly lowers the core body temperature and potentially leads to mild hypothermia.
Essential Safety Measures for Cold Weather Tubbing
Mitigating the risks of cold-weather tubbing involves addressing both chemical and physical challenges. Regular testing and adjustment of the water chemistry is the most important step in preventing waterborne illnesses. Maintaining proper sanitizer and pH levels ensures that pathogens like Legionella and Pseudomonas are controlled.
Users should minimize their soak time, limiting sessions to 20 minutes or less, to reduce internal body temperature rise and chemical exposure. Upon exiting, a rapid and prepared retreat is necessary to manage physiological stress. Have a heavy robe, warm slippers, and a dry towel immediately accessible so you can quickly cover up and minimize the exposure of wet skin to the cold air.
Avoiding alcohol consumption before or during a soak is also advised. Alcohol impairs judgment and accelerates peripheral vasodilation, increasing the risk of heat-related illness and rapid core temperature drop upon exit.