Health. Heatwave: Can you really get sick from air conditioning or a fan?

Suffering from a cold, headache, or stiff neck during a heatwave ? Many people believe the culprit is obvious: air conditioning and fans tend to make us sick. However, this popular belief needs to be qualified.

First, let's remember that you can't be directly infected by a virus like the common cold from air conditioning or ventilation. Air circulation does not, in and of itself, produce viral agents. Transmission always occurs from one infected person to another, via droplets, physical contact, or contaminated objects.

Now that the basics are out of the way, it's important to note that cold weather, and especially sudden temperature changes (more than five to seven degrees Celsius difference from outside), weakens our immune system. Air conditioning doesn't help, because by cooling the air, it also dries it out. As a result, our mucous membranes (mouth, nostrils, larynx) become irritated, which can cause coughing or a runny nose, or even make us more vulnerable to germs.

Dry air will also cause "an acceleration of the evaporation of the tear film," adds ophthalmologist ^Dr. Mehdi Cherif. If this layer that protects our eyes is no longer moist, "stinging, burning, and a sensation of grains of sand" are to be feared, especially in "contact lens wearers, the elderly, or post-operative patients."

"People with respiratory illnesses are also more sensitive," says ^Dr. Frédéric Le Guillou, a pulmonologist and allergist. For example, a fan stirring up dust can easily bother people with dust mite allergies. Also, beware of neck pain, as the sensation of cold can cause muscle contractions.

But the president of the French Respiratory Health Association (Santé Réspiratoire France) warns above all of "the risk of contamination with bacteria, fungi, and mold," particularly in air conditioning systems. The latter actually forms condensates, or small amounts of water, which can become "a breeding ground for microbes." Among them: legionella, the bacteria responsible for Legionnaires' disease, a potentially serious respiratory illness.

^Dr. Mehdi Cherif, from OphtaMaine, emphasizes "microparticles that can get into a fan and can cause eye infections." "This can lead to conjunctivitis, or even keratitis, which is damage to the cornea," he explains. "Most of the time, it's misuse or poor maintenance that can cause symptoms," ^Dr. Le Guillou reassures. To avoid these problems, remember to regularly clean your fan blades and change your air conditioning filters, whether at home or in your car. It's even "crucial," insists the pulmonologist-allergist.

"You should also try to humidify the air," adds his colleague. ^Dr. Mehdi Cherif advises maintaining a humidity level "around 40%," for example, by placing a damp cloth or a bowl of water near your fan. Be careful, however, of electrocution! The doctor also recommends "not directing the fan's airflow toward your face, especially when sleeping," "drinking enough to maintain good body hydration," and even "lubricate your eyes with artificial tears."

Above all, keep in mind that natural ventilation should always be favored over electrical appliances. Especially air conditioning, which is disastrous for the environment. Engineer Hakim Hamadou points out on the Ademe website that "if everyone installs air conditioning in the city and sets it to 23°C, we will increase the outside air temperature by 2 to 3.6°C by 2030." In short, in the long term, we will only make the situation worse.

The Heatwave Info Service hotline can be reached at 0800 06 66 66, from 8 a.m. to 7 p.m. (free call from mainland France).