Extended periods in air-conditioned indoor spaces can cause respiratory irritation, dry skin, and an increased susceptibility to infections [1, 2].

These health risks emerge as people spend more time in mechanically cooled environments during summer heat spikes. Because air conditioning lowers indoor humidity and recirculates stale air, it can exacerbate existing lung conditions and spread pathogens [1, 2].

Medical professionals note that the moisture loss caused by these systems affects the body's natural defenses. “Running an air-conditioner for long periods can dry out the mucous membranes in your nose and throat, making you more vulnerable to viruses,” said Dr. Aisha Khan, a pulmonologist [2].

This vulnerability is particularly acute for specific patient groups. Prof. Maya Patel said that people with interstitial lung disease are especially at risk when indoor air is overly dry and cold [3].

The physical impact of continuous exposure is measurable. Roughly 38% of people report experiencing dry skin after more than six hours of continuous AC exposure [2]. Furthermore, there is a 12% rise in respiratory-related doctor visits during peak AC season compared with non-summer months [2].

To mitigate these risks, experts suggest monitoring thermostat settings. While some sources suggest 22 °C (72 °F) to prevent heat-related illness [2], a research team from Energy Canada said the optimal setting for health and energy savings is around 24 °C (75 °F) [1].

“Anything lower for extended periods can increase the risk of respiratory irritation,” the Energy Canada team said [1].

““Running an air-conditioner for long periods can dry out the mucous membranes... making you more vulnerable to viruses.””

The tension between preventing heatstroke and avoiding respiratory irritation suggests that indoor climate control is not a one-size-fits-all solution. As global temperatures rise, the reliance on mechanical cooling creates a secondary public health challenge where the environment intended to protect users from external heat may inadvertently weaken their immune defenses and aggravate chronic lung diseases.