Adverse health effects of high humidity

Humidity refers to the amount of water vapour present in the air at any given time. High humidity levels can result in temperatures feeling higher than they actually are. High levels of moisture in the air causes sweat to evaporate from the human body at a much slower rate than normal. The human body reacts to high humidity by trying to cool down through the process of perspiration. When this fails, the body continues to heat up, leading to dehydration and potential health problems.


High humidity levels can increase the level of allergens floating around your home. Dust mites flourish in high humidity environments, as do mould spores that develop on walls and ceilings. Both can present a real problem to allergen sufferers whose conditions can significantly worsen in high humidity environments.

Risk groups

The potential harm that can result from high humidity varies depending on an individual's weight, age and general physical health. Elderly people are more at risk as the condition of their internal organs and muscles tends to be weaker than younger people. However, younger people undertaking strenuous physical activity in humid conditions can suffer nausea, headaches, fainting and accelerated pulse rates.

Raised body temperature

As the body’s water supplies deplete, it has insufficient moisture levels to sweat at the required rate. This causes the blood to thicken, meaning more pressure is needed to keep blood circulating around the body. This places added pressure on both blood vessels and the heart and can lead to reduced bloody supply to the brain, muscle groups and internal organs.

Heat cramps and fainting

Physical activity in humid conditions can lead to severe imbalances in the body’s salt levels. This can result in severe muscle cramps, especially in the legs. Adapting to heat levels over time and maintaining regular fluid intake usually reduces the severity of these cramps. Fainting is another significant risk of exercising in high humidity and is triggered by a fast drop in the body’s blood pressure. Lessening your level of exertion during exercise in humid conditions will reduce your risk of fainting.

Heat exhaustion

Heat exhaustion occurs when body temperature rises to around 102C (215F) and is caused by a substantial loss of body fluid and salt. Heat exhaustion can lead to hospitalisation, particularly among the elderly. Heat exhaustion can be difficult to identify as it often occurs days after a heatwave rather than at the time.


Heatstroke occurs when body temperature reaches around 105C (221F). Victims typically become confused and lethargic and may lapse into unconsciousness. Heatstroke is an extremely serious, potentially fatal condition. Medical aid should be sought immediately if heatstroke is suspected. Consuming plenty of fluids and taking cool-off breaks when you feel fatigued or experience headaches can help reduce the likelihood of heatstroke.

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About the Author

Jason Prader began writing professionally in 2009, and is a freelance writer with a sound academic background and experience in writing articles for online magazine He is highly adept at constructing academic essays and producing articles on an array of subject matter. He holds a master's degree in 20th century literature from the University of Sussex.