World Health Day 2026 | The cold truth about your AC: Why your air conditioner is giving you a ‘summer cold’

As the mercury climbs toward 35degree Celsius the hum of an air conditioner becomes the soundtrack of survival Indians retreat into our chilled sanctuaries seeking refuge from the sweltering humidity But for many that relief comes at a cost a scratchy throat a persistent sniffle and a foggy headmdashthe dreaded summer coldIs the AC actually making you sick or is it just a coincidence This World Health Day Dr Divya Gopal additional director of internal medicine at Sir HN Reliance Foundation Hospital and Dr Nilesh Sonawane consultant pulmonologist at Apollo Clinic decode why our cooling systems sometimes turn into irritant machinesThe thermal shockThe most common cause of feeling sick from an AC isnt a germ at allmdashits physics When you move between the 35 degrees Celsius heat of a Mumbai or Pune afternoon and a 20 degrees Celsius office your body undergoes a thermal shockDr Gopal explains that your respiratory liningmdashthe delicate mucous membrane inside your nose and throatmdashis built for gradual transitions not sudden plunges When you step out of 35 degrees Celsius heat into a freezing 20 degrees Celsius office or car your blood vessels in the nose go into a mini panicThey first constrict to conserve heat and then dilate rapidly as your body tries to adjust This is basically vasomotor rhinitis in action The result Your lining swells extra mucus pours out and you get a stuffy runny nose without a single virus in sight Over time this repeated shock stresses the ciliamdashthe tiny hairlike structures that sweep out dust and germsmdashmaking your respiratory tract inflamed and hyperreactive she warnsThe humidity trap Why dry air invites virusesWhile we celebrate ACs for removing sticky humidity they often go too far A healthy nose thrives in 40ndash60 per cent humidity AC units however can strip that moisture down to a bonedry 20ndash30 per centDr Sonawane notes that this dry environment is responsible for the lionrsquos share of uncomfortable symptoms like sore throats and dry coughs Air conditioning systems are used to cool indoor spaces by removing heat and moisture This dry environment is responsible for many uncomfortable symptoms The colder you set your air conditioning the more likely you are to increase dryness and irritation he explainsDr Gopal takes it a step further describing the mucus in your nose as a security system ldquoWhen the air is dry that mucus thickens or cracks creating an easy landing strip for actual viruses Suddenly a mild virus that your body would normally flush out can settle in and multiply Patients often find their symptoms vanish the moment they step back into the humid outside airmdasha clear sign the AC was the culpritrdquo she addsMaintenance versus microbesIf your symptoms include sneezing fatigue or a persistent cough the culprit might not be the temperature but the machines hygiene Experts estimate that 30ndash40 per cent of summer cold cases are actually caused by what is growing inside the unitDust pollen and moisture collect on filters and evaporator coils turning them into what Gopal calls a cozy hotel for mould fungi and bacteria When the AC blows it aerosolises these particles straight into your breathing zone Mould spores trigger allergictype inflammation that feels exactly like a cold Temperature and dryness get the blame but dirty maintenance turns your AC from a friend into a lowgrade irritant machine she statesDr Sonawane agrees emphasising ldquoDirty filters recirculate dust and animal dander which can lead to bronchospasm a spasm of the bronchial muscles in people with asthma or preexisting respiratory conditions While Legionella bacteria are rare in residential split AC systems they can thrive in poorly maintained cooling towers of large offices or hotelsrdquoFinding the sweet spotSo how do we stay cool without getting sick The doctors agree on a safe deltamdashthe maximum temperature difference between the indoors and outdoors1 The 810 degrees Celsius rule Gopal recommends keeping the gap between indoor and outdoor temperatures to no more than 10 degrees Celsius If itrsquos 40 degrees Celsius outside donrsquot aim for 20 degrees Celsius immediately2 The sweet spot Both experts identify 2426 degrees Celsius as the ideal rangeFinding a temperature range of 2426 degrees Celsius is far more appealing to most consumers and helps to create a balance between temperature and moisture in the air Setting the AC here will offer comfort and greatly reduce the chances of irritating your throat says Dr SonawaneDoctorapproved strategies for a healthy summerTo prevent the AC from compromising your health follow this checklist of expert approved tips1 Acclimatise gradually Dont blast it arcticcold the moment you walk inside Gopal suggests giving your body 30ndash60 minutes to acclimatise If itrsquos exceptionally hot start your AC at 28 degrees Celsius and slowly bring it down to the sweet spot2 Hydrate internally and externally Use these tips Drink up Sonawane emphasises drinking plenty of fluids to keep the throat moist and less prone to irritation Warm relief If you already have an irritated throat he suggests warm or hot liquids like soup and tea which provide immediate relief to the mucous membranes The humidifier hack Gopal suggests a small humidifier in the bedroom if the air feels too dry Alternatively inhaling steam can help rehumidify the airway directly3 Master your night mode Leaving the AC on a low setting all night is a recipe for a morning sore throat Use sleep mode This allows for gradual temperature changes while you sleep The fan switch Sonawane recommends using the AC to cool the room down initially then switching to a ceiling fan or using a timer to prevent excessive cooling throughout the night4 Break the cycle Dont live in a sealed box Sonawane advises taking breaks from the AC and opening windows periodically to allow for crossventilation This reduces the accumulation of indoor pollutants and recycled air containing dust and allergens5 Avoid direct blast Position your workstation or bed so you arent sitting directly in front of the unit Direct exposure to the cold stream can lead to localised irritation and even muscle spasms in the bronchial tubes for sensitive individualsIrritant or infection How to tell the differenceIt is critical to recognise whether you are suffering from a simple environmental irritant or an actual acute viral infection Here is how the doctors differentiate the twoAC irritation vasomotor rhinitis1 Typically manifests as a dry acrid or slightly scratchy throat2 Symptoms often include a stuffy or runny nose that appears suddenly when entering a cold room3 Symptoms usually vanish or significantly improve the moment you switch off the AC or step into humid air4 Generally lacks systemic symptoms like high fever or severe body achesViral summer cold1 Presents with classic infection markers fever muscle pain and deep fatigue2 Congestion and runny nose persist regardless of whether the AC is on or off3 Symptoms typically linger for more than a week4 May involve a productive cough or significant respiratory distressDr Gopal suggests being vigilant when it comes to experiencing the above symptoms ldquoIf symptoms linger more than a week or you get fever and body aches come see your doctor sometimes it really is a virus riding on top of the AC irritationrdquo Sonawane adds ldquoWhen used correctly air conditioning will be able to provide comfort as well as prevent harm to ones respiratory system The primary goal should be to increase moisture and decrease the amount of dry air Treat your AC rightmdashclean the filters mind the thermostat and stay hydratedmdashand you can enjoy a cool summer without the tissue boxrdquo