OVERVIEW

What is air conditioning sickness?

The invention of air conditioning has created a comfortable living environment for humans, but its negative impact on health has increasingly drawn attention.

People who spend long periods in air-conditioned environments often report poor indoor air quality, followed by symptoms such as itchy eyes, coughing, chest tightness, dry or itchy skin, fatigue, headaches, dizziness, and abnormal taste or smell.

This occurs because air pollution in certain buildings, combined with low air exchange rates, leads to a series of symptoms among occupants. These symptoms typically subside after leaving the building.

This is commonly referred to as "air conditioning sickness," also known as air conditioning syndrome, tight building syndrome, office sickness, sick building syndrome (SBS), or building-related illness.

Such buildings are also called "sick" or "unhealthy" buildings. More internationally standardized terms are "building-related symptoms" and "building-related illness."

Why do some doctors say air conditioning sickness doesn’t exist?

"Sick building syndrome" was first proposed by foreign experts in recent years, while in China, it is often called "air conditioning syndrome" or "air conditioning sickness."

However, this term has limitations and may imply that the building is "sick" rather than the people. Over time, it has become clear that symptoms or illnesses clearly linked to buildings are actually very common.

For these reasons, terms like "sick building syndrome," "air conditioning syndrome," or "air conditioning sickness" are rarely used in current literature. Instead, two more patient-centered terms have emerged: "building-related symptoms" and "building-related illness."

Therefore, medically, "air conditioning sickness" is not a formal or commonly used disease name. It is merely a collective term used in China to describe a series of similar symptoms caused by poor building ventilation (often due to air conditioning use).

The lack of a standardized disease name does not mean "air conditioning sickness" doesn’t exist. Currently, "building-related symptoms" and "building-related illness" have become standard medical terms. For familiarity and convenience, we will still use "air conditioning sickness" below.

Is air conditioning sickness common?

Building-related illnesses and symptoms are very common. Some studies and reports on "sick building syndrome" have investigated symptoms and illnesses caused by non-industrial work environments, with up to 60% of workers reporting at least one symptom related to their workplace.

Does air conditioning sickness affect health?

Symptoms and illnesses attributed to indoor environments are common. Various factors between the environment and individuals influence these symptoms, potentially triggering new illnesses, worsening pre-existing conditions (e.g., rhinitis, asthma), or causing workplace-specific diseases (e.g., occupational asthma, hypersensitivity pneumonitis).

In the industrial and information age, people spend about 22 hours a day indoors studying, working, and living. Urban residents spend approximately 80%–90% of their lives indoors.

The quality of indoor air directly impacts health. Increasingly sealed buildings reduce ventilation, and factors like smoking further worsen indoor air pollution.

In summary, building-related symptoms/illnesses can significantly affect health.

SYMPTOMS

What are the symptoms of air-conditioning sickness?

In specific building environments (primarily enclosed air-conditioned indoor spaces), indoor air quality is affected by pollutants emitted indoors and outdoor air quality, among other factors. The resulting symptoms and illnesses are categorized as "building-related symptoms" and "building-related illnesses."

What are building-related illnesses?

Building-related illnesses are diseases associated with specific buildings or indoor environments and meet the diagnostic criteria for particular conditions. The severity of these illnesses varies and includes, but is not limited to, the following:

• Rhinitis, asthma, respiratory irritation (triggered by irritants or allergens, recurring or worsening, and linked to the environment)

• Eczema and dermatitis (common causes include low humidity, dry skin, or contact allergies)

• Hypersensitivity pneumonitis

• Allergic conjunctivitis, dry eye syndrome, conjunctivitis

• Legionnaires' disease caused by Legionella pneumophila (related to unclean air-conditioning systems, such as dirty filters)

• Influenza, common cold, tuberculosis

• Carbon monoxide poisoning

What are building-related symptoms?

Building-related symptoms are symptoms experienced by individuals in specific buildings that are not easily classified as a particular illness. Compared to "building-related illnesses," "building-related symptoms" are more commonly referred to as or equated with "air-conditioning sickness."

Building-related symptoms typically begin after entering a workplace building and may improve or disappear upon leaving. In cases of allergies or asthma, reactions can sometimes be delayed by several hours. Over time, symptoms may become more frequent, persistent, or easily triggered.

Common building-related symptoms include:

• Mucous membrane irritation: Itchy, watery, or dry eyes; nasal congestion or runny nose; dry or itchy throat.

• Chest symptoms: Cough, chest tightness, difficulty breathing, wheezing, or even the need for asthma medication.

• Skin symptoms: Rash, dry or itchy skin.

• General or neurological symptoms: Fatigue, difficulty concentrating, headache, dizziness, muscle pain.

• Sensory symptoms: Abnormal taste or smell, heightened sensitivity to strong odors.

CAUSES

Why is air conditioning sickness more likely to occur in air-conditioned indoor environments?

Impact on indoor microclimate:

• Although air conditioning can improve indoor microclimate and comfort, the airtight environment of buildings leads to poor ventilation, preventing the replenishment of fresh outdoor air. Prolonged exposure to such conditions can cause various discomforts.
• If relative humidity is controlled above 70%, it may cause chest tightness, while levels below 30% can lead to dry skin and mucous membranes, resulting in irritation symptoms.

Effects of indoor lighting and noise:

• Due to the sealed nature of air-conditioned buildings, insufficient natural lighting, the use of energy-saving lamps, and the widespread presence of household appliances like computers, refrigerators, TVs, and microwaves, the noise generated by these devices can cause discomfort. Symptoms often include headaches, fatigue, and difficulty concentrating, affecting general well-being or the nervous system.

Individual, gender, age, and regional differences in thermal stress responses:

• Studies on thermal stress responses show that women tolerate humid and hot environments better than men.
• Young people adapt better to cold and hot environments than the elderly, as older individuals sweat later in hot conditions. Infants and young children have underdeveloped thermoregulation systems, making them highly sensitive to temperature changes.
• Thus, prolonged exposure to air-conditioned environments poses greater cardiovascular risks for the elderly and infants. Sudden temperature shifts between indoor and outdoor settings can easily trigger symptoms like runny nose, nasal congestion, chest tightness, and coughing.

Where is air conditioning sickness most likely to occur?

Schools, offices, and factories:

• Poor ventilation is a common issue in many schools, which are also hotspots for dust, allergens, cleaning products, and mold. Outbreaks of infectious diseases, especially viral illnesses, are frequent in such environments.
• Similarly, offices and factories, being poorly ventilated and densely populated, pose risks. Adults generally have stronger immune systems, making them less susceptible to common contagious diseases.

Restaurants and entertainment venues:

• High-risk locations include bars, restaurants, cinemas, KTVs, and other hospitality or entertainment venues, particularly where secondhand smoke or cooking fumes may act as respiratory irritants.

Healthcare facilities:

• Workers in healthcare settings are exposed to numerous allergens and irritants, such as rubber gloves, respiratory pathogens, and bloodborne pathogens.
• Other hazards include medications (e.g., herbal remedies, antibiotics, chemotherapy drugs, aerosolized medications), disinfectants, and cleaning products, many of which are strong irritants.

DIAGNOSIS

How to diagnose air conditioning sickness?

Building-related symptoms can be clinically diagnosed when symptoms alleviate after leaving the corresponding building. However, most people with building-related symptoms have underlying conditions or suffer from building-related illnesses such as rhinitis, allergic conjunctivitis, and/or asthma. Therefore, a doctor should first rule out other possible diseases during diagnosis.

TREATMENT

Which department should I visit for air conditioning sickness?

If symptoms related to "air conditioning sickness" persist after leaving the building, you can visit the general internal medicine department. Alternatively, depending on the affected area, you may seek treatment at otolaryngology, dermatology, respiratory medicine, neurology, cardiology, or gastroenterology departments.

How to relieve air conditioning sickness symptoms?

For "building-related illnesses," visit the relevant department for symptomatic or cause-specific treatment.

For "building-related symptoms," the following measures in daily life and work can help alleviate symptoms:

Ventilation:

• Improve air quality through mechanical or natural ventilation. For health and comfort, the outdoor air supply rate should be as high as 25 liters per second per person. Ventilation rates below 10 liters per second may increase building-related symptoms. Therefore, mechanical ventilation systems must meet qualified standards.

• If outdoor air is polluted, mechanical ventilation systems should use filters to limit fine smoke particles, allergens, and other particulates. Filter efficiency varies, so regular maintenance (cleaning or replacement) is necessary for effectiveness.

• While most buildings have fixed ventilation systems, regular maintenance can still be requested or supervised. If air conditioning sickness symptoms are severe and widespread, improvements to ventilation efficiency can be proposed.

Temperature:

• Temperatures above 22–23°C are associated with worsened symptoms, including mucosal irritation, headaches, and fatigue. Optimal temperatures vary by season.
• The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommends winter temperatures between 20–24°C and summer temperatures between 22–26°C. In high humidity, the lower end of this range is preferable.

Humidity:

• Low indoor relative humidity (<30%) is linked to dry eyes, upper respiratory symptoms, and skin irritation. High humidity (>60–65%) may promote microbial growth or condensation, causing symptoms.
• ASHRAE suggests maintaining humidity between 30%–60% for comfort. The U.S. Environmental Protection Agency (EPA) further recommends keeping relative humidity <60% to inhibit mold growth and <50% to reduce dust mites. For individuals with rhinitis or asthma, 40%–50% humidity is ideal.

Green Buildings:

• Adopt eco-friendly building designs and standards, including low-toxicity or chemical-free (volatile organic/inorganic compounds) materials, furnishings, and furniture.

Reduce Indoor Air Pollution:

• Minimize controllable indoor pollutants such as cleaning/disinfecting products, secondhand smoke, strongly scented foods, perfumes, pet dander, and dust.

Psychosocial Work Factors:

• Employees who feel overworked, under-stimulated, or lack control over their work environment (including physical conditions) with little colleague support often experience more indoor air and work-related symptoms. Proper work-life balance and stress relief can help reduce or alleviate symptoms.

DIET & LIFESTYLE

What should air-conditioning syndrome patients pay attention to in their diet?

There are no special dietary restrictions, just maintain a healthy and balanced diet.

• When cooking, use less salt, less oil, and fewer high-salt seasonings. Avoid pickled vegetables and meats;

• Do not rely solely on refined rice and white flour for staple foods. Replace some with whole grains, mixed beans, potatoes, pumpkins, etc.;

• Balance meat and vegetables. Prefer white meats like chicken, duck, and fish, and limit fatty meats. Eggs and milk are important sources of protein and other nutrients;

• If vegetarian, eat more beans and bean products to supplement protein;

• Consume plenty of fruits and vegetables;

• Avoid alcohol as much as possible.

What should air-conditioning syndrome patients pay attention to in daily life?

There are no special lifestyle precautions, just maintain healthy habits, such as:

• Do not smoke;

• Exercise regularly, avoid prolonged sitting, and prevent overweight and obesity;

• Exercise 3–5 times a week for about 30 minutes each session, combining aerobic and strength training at a moderate intensity without overexertion;

• Ensure sufficient sleep daily, whether going to bed early or late;

• Learn to manage stress and emotional tension.

PREVENTION

How to Prevent Air Conditioning Sickness?

Refer to the relevant measures in the treatment recommendations, and you can adopt the same methods at home:

• When using air conditioning, keep the temperature between 20–24°C in winter and 22–27°C in summer;

• Maintain a humidity level of 40%–50%, which is more comfortable;

• Have professionals regularly repair and clean the air conditioner, at least once a year;

• Turn off the air conditioner and open windows for ventilation when appropriate;

• Develop habits of drinking water frequently and moisturizing your skin;

• Choose eco-friendly building materials and furniture;

• Reduce or strictly prohibit indoor smoking;

• Balance work and rest, maintain a reasonable schedule for work, rest, and exercise, increase outdoor time, and live a healthy lifestyle.