How seasonal changes weaken immunity and what experts recommend to stay healthy

As the seasons change, so does the way our bodies respond to infections. Autumn and winter, in particular, are linked to a rise in respiratory illnesses and other contagious diseases, highlighting the importance of understanding how seasonal factors influence immunity.

Experts say that temperature fluctuations, lower sunlight exposure, and lifestyle changes during colder months can make people more susceptible to illnesses ranging from the common cold and flu to childhood infections like mumps and pertussis.

How seasons impact the immune system

Dr Tushar Tayal, Associate Director of Internal Medicine at CK Birla Hospital, Gurugram, explains that the human immune system, though sophisticated, is highly sensitive to environmental factors. “Unpredictable changes in weather stress the body, making it harder for the immune system to operate at its best,” he says.

Cold temperatures constrict blood vessels, reducing the delivery of infection-fighting white blood cells, while dry air can parch the mucous membranes in the nose and throat, limiting their ability to trap and neutralize viruses.

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Seasonal shifts also coincide with higher viral activity. Influenza and cold viruses replicate more efficiently in colder, drier conditions. “During these months, people spend more time indoors, often in poorly ventilated spaces, which increases the risk of infections spreading through shared surfaces or close contact,” Dr Tayal adds.

Vitamin D, sunlight and immune health

Shorter days and reduced sunlight during autumn and winter can lead to vitamin D deficiency, which is crucial for regulating immune responses and reducing inflammation. Dr Tayal notes that this deficiency can leave the body more vulnerable to respiratory infections. “Vitamin D aids control over immune response and decreases inflammation, so lower levels make it easier for infections to take hold,” he says.

Lifestyle, stress and immune overload

Seasonal changes also often disrupt daily routines. Reduced physical activity, irregular diets, poor sleep, and rising stress levels due to work, school schedules, or holidays can suppress immunity, creating additional vulnerability to infections.

“Chronic stress is immunosuppressive, and combined with seasonal environmental changes, it becomes easier for diseases to establish themselves,” Dr Tayal explains.

Tips to stay healthy during seasonal transitions

*To mitigate the impact of seasonal changes on health, experts recommend:

*Staying well-hydrated to keep mucous membranes moist

*Dressing appropriately to avoid sudden temperature shocks

*Maintaining a balanced, nutritious diet

*Supplementing with vitamin D if sunlight exposure is limited

*Practicing good hygiene, especially frequent hand washing

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Managing stress through mindfulness, exercise or relaxation techniques

Dr Tayal emphasises that while seasonal changes are a natural part of life, awareness and preventive measures can help maintain immunity and reduce the risk of infection. “Understanding how weather and lifestyle changes affect the immune system allows us to take proactive steps to stay healthy throughout the year,” he says.