“I caught a cold from the air conditioner,” “I sat under the AC and got sick” — you’ve probably heard these phrases, or perhaps you’ve noticed that after spending several hours in an air-conditioned room, your throat starts to feel scratchy, your nose becomes blocked, or you develop a runny nose.
Can air conditioning really cause a cold? The short answer is no.
The common cold is a viral infection. It is caused by viruses, not by cold air, drafts, or air conditioning.
However, air conditioning can affect how you feel. Cold or dry air can irritate the mucous membranes of the nose and throat, while poor ventilation can contribute to the spread of respiratory viruses.
Why Can Air Conditioning Cause Nasal Congestion or a Sore Throat?
Imagine a typical situation: it’s +35°C outside, while your office is cool and the air conditioner is running.
After a few hours, you notice:
- Dryness or a scratchy feeling in your throat;
- Nasal congestion and a feeling of dryness in your nose;
- Eye irritation;
- Discomfort caused by cold air.
This does not necessarily mean you have become ill. Dry air can irritate the mucous membranes of the respiratory tract, so unpleasant symptoms may occur even without an infection. This is particularly noticeable when you spend a long time in a room with very dry air or when the airflow is directed straight at your face.
What If You Develop a Runny Nose, Cough, and Fever After Using Air Conditioning?
In this situation, an infection is much more likely than a “cold caused by cold air.” Respiratory viruses are transmitted from person to person. Common cold symptoms may include a runny nose, nasal congestion, a sore or scratchy throat, coughing, and sometimes an elevated temperature. However, exposure to an infection and the onset of symptoms do not always occur at the same time.
The fact that you “sat under the air conditioner in the evening and became ill overnight” does not mean that the air conditioner caused your illness. Most likely, you acquired the infection earlier, and the onset of symptoms simply coincided with the time you spent in the cool air.
Cold air does not make viruses in your body more dangerous, nor does it create an infection out of nothing.
Is It Safe to Sit Directly Under an Air Conditioner?
There is no strict medical prohibition against it. However, if the cold airflow causes discomfort, throat dryness, or a feeling of nasal congestion, it is better to redirect the airflow or increase the temperature slightly. This is primarily a matter of comfort rather than cold prevention. There is no universal rule requiring an air conditioner to be set to a specific temperature to prevent illness.
What Matters More Than the AC Temperature? Ventilation!
This is where air conditioning and ventilation can genuinely influence the risk of respiratory infections. In enclosed spaces, viral particles can accumulate in the air. Good ventilation helps remove them from the room and reduce the concentration of airborne viral particles.
However, air conditioning and ventilation are not the same thing. An air conditioner may simply cool and circulate indoor air without providing an adequate supply of fresh air.
In a crowded office or a poorly ventilated room, the risk of respiratory infection is primarily associated with contact between people and air quality, not with the fact that the air is cold.
Can You Catch an Infection from the Air Conditioner Itself?
An ordinary home or car air conditioner is not some special “breeding ground for viruses.” For the spread of respiratory infections, it is much more important how many people are in the room, how well it is ventilated, and how close people are to one another.
There is no need to be afraid of using air conditioning in summer. It is much more useful to:
- Have the equipment regularly serviced and cleaned;
- Check and maintain the filters according to the manufacturer's instructions;
- Ensure a supply of fresh air whenever possible;
- Avoid spending long periods in stuffy, overcrowded spaces.
What Should You Do If Your Throat Feels Scratchy After Using Air Conditioning?
If you do not have a fever, feel generally well, and the discomfort started after spending several hours in a dry or cold environment, simple measures are usually sufficient:
- Drink enough fluids when you feel thirsty.
- Redirect the airflow so that it does not blow directly onto your face.
- Ventilate the room if possible.
- Do not try to treat ordinary mucosal irritation with antibiotics. Antibiotics do not work against viruses and are not needed for the common cold.
If your symptoms improve after you leave a room with dry or cold air, this may also suggest irritation of the mucous membranes rather than an infection.
What About Legionnaires’ Disease?
You may have heard that air conditioning can be associated with Legionnaires’ disease. This is true, but it does not apply to every air conditioner. Legionnaires’ disease is an infection caused by the bacterium Legionella. It grows in water. For a person to become infected, the bacteria usually need to enter the respiratory tract in tiny droplets of contaminated water that form an aerosol.
The risk is not associated with the cold air blown out by an air conditioner, but with certain systems in which water circulates.
Where Can This Risk Actually Occur?
The risk is primarily associated with large building cooling systems, such as cooling towers and evaporative cooling systems, which use water. If these systems are not properly maintained, the water can become a source of Legionella, and the resulting aerosol can spread the bacteria into the surrounding air. Such systems have been linked to outbreaks of Legionnaires’ disease.
Other potential sources of Legionella include certain hot and cold water systems, showers, hot tubs, decorative fountains, and humidifiers.
What about an ordinary air conditioner at home or in your car? There is no need to fear it because of Legionella.
A typical household air conditioner cools the air and is not a common source of Legionella infection. The problem primarily arises in large water systems that can generate aerosols and are inadequately maintained. Therefore, the association between air conditioning and Legionnaires’ disease does not mean that every air conditioner in an apartment, car, or small office poses a danger.
It is similar to saying that “water can be a source of infection.” That is true, but it does not mean you should be afraid of every glass of water.
When Might the Air Conditioner Not Be the Cause?
This is perhaps the most important question. If your symptoms are severe or persistent, do not automatically blame the air conditioner.
Seek medical attention if:
- You develop shortness of breath or difficulty breathing;
- You experience chest pain or significant chest discomfort;
- A high fever persists for several days;
- Your symptoms noticeably worsen;
- You initially improve but then develop a fever again or your cough becomes more severe;
- Cold symptoms persist for more than 7–10 days without improvement;
- A chronic condition worsens;
- You feel significantly worse than you would with an ordinary mild cold.
If you frequently become ill, your symptoms seem unusual each time, or you are unsure whether you actually have a cold, a medical consultation can help identify the cause.
Sometimes, what people call a “cold from the air conditioner” may actually be allergic rhinitis, bronchial asthma, reflux, or another condition.
Air conditioning is not the enemy of your health. The key is a comfortable temperature, proper ventilation, and paying attention to your symptoms.