You know the feeling: You turn on the air conditioning on a hot summer day and suddenly find yourself sniffling, coughing, or sneezing. You wonder to yourself, “Could I be allergic to the AC?”

The short answer is no. However, you can be allergic to the quality of the air circulating through your air conditioning unit.

While your air conditioning isn’t what’s making you sick, it can circulate air contaminants that are the root of your issues. The unit itself may even house the problem.

If you start to feel unwell when you turn on the air conditioning, several airborne allergens could be to blame. Air conditioning units can also spread bacteria and viruses.

Biological contamination can cause allergic reactions, including hypersensitivity pneumonitis, allergic rhinitis, and asthma.

In large buildings, toxins released by microorganisms that live in the ventilation system can affect people. Symptoms of reactions to air contamination can include:

  • sneezing
  • coughing
  • tiredness
  • dizziness
  • fever
  • shortness of breath
  • watery eyes
  • digestive issues

Older people, children, and those with existing respiratory issues are more susceptible to the effects of airborne contaminants.


Many people are allergic to various types of pollen. Pollen comes from plants and can be found inside buildings. It can get inside through open doors and windows, but it can also be tracked into buildings on shoes or clothes.

Pollen particles are usually large enough to settle onto surfaces, but can be disturbed by air flow and stay suspended in the air for hours.

An effective way to decrease indoor levels of pollen is to keep windows and doors closed.

Dust mites

Dust mites feed primarily on human skin and are commonly found in homes or other buildings. They can breed inside your air conditioner.

These organisms like to reproduce in warm, damp conditions. According to Berkeley Lab, 40 to 50 percent maintained relative humidity decreases dust mite prevalence.

Pet dander

Pet dander contains proteins to which some people are allergic. It’s possible to develop an allergy later in life. Pet dander can go airborne, and your AC unit can circulate the dander, resulting in allergy symptoms.

Dander can be minimized by washing your pets regularly. If this doesn’t help, you may want to consider medications like allergy shots.

Mold and mildew

Your air conditioning unit may be a breeding ground for mold and mildew. These organisms flourish in damp environments. If your AC unit has a damp or wet cooling coil, humidifier, or condensate pan, you can develop a mold or mildew problem.

Mold and mildew can release toxins that cause an allergic reaction or even disease.

Bacteria and viruses

People and animals can carry bacteria or viruses into the home, or they can come inside from soil and plant debris. Certain bacteria and viruses can be transmitted through the air. Your air conditioning unit could circulate them, causing you to become ill.

Airborne bacteria and viruses include:


Air pollution is often thought of as something you find outdoors, but air pollution is also commonly found inside. It can cause coughing, agitate asthma, and decrease lung function.

Consider an air purifier or purifying plants for indoor air pollution.

Volatile organic compounds (VOCs)

VOCs are the result of off-gassing chemicals. They can come from a range of products including household cleaning supplies.

Your air conditioning unit can circulate these toxic gasses, especially if cleaned with these products. Review the cleaners that you’re using and look for safe alternatives.

If you feel ill as a result of indoor air contamination, rather than treat your symptoms, you should treat your home:

  • Replace your air filters. (HEPA filters can remove 99.9 percent of particles above a certain size.)
  • Clean registers and return vents (the intake and output vents).
  • Clean the ductwork below or above your home.
  • Clean dust and debris, including around the outdoor AC unit.
  • Keep an eye out for mold, and remove it promptly.
  • Get an air purifier.
  • Control the relative humidity in your home to block the growth of biological organisms.
  • Remove any standing water, water-damaged materials, or wet surfaces to prevent the growth of mold, mildew, bacteria, and mites.
  • Have your air conditioning ducts professionally cleaned.

Most issues that come from air conditioning are the result of airborne contaminants. However, in some rare cases, the cold air from air conditioning can cause skin reactions.

In one documented instance, a woman developed hives when her co-workers turned on the air conditioning.

The condition that causes this is known as cold urticaria: Exposure to cold temperatures results in hives appear on the skin within minutes. In some instances, cold urticaria can cause swelling.

Another severe reaction to this condition is anaphylaxis, which can result in fainting, heart racing, the swelling of the limbs or torso, and shock.

The worst cases of cold urticaria occur when there is full skin exposure to cold. Swimming in cold water can be life-threatening for those with cold urticaria, as it can result in low blood pressure, fainting, or shock.

Symptoms of cold urticaria range from minor to severe, and this condition most often occurs in young adults.

It’s recommended that those with cold urticaria protect their skin, avoid exposure to cold air or water, and avoid contact with cold items or surfaces. Damp and windy conditions can cause symptoms of this condition to flare.

If you experience a skin reaction after cold exposure, even if the reaction is mild, talk to a doctor. Seek medical help if you experience anaphylaxis or have difficulty breathing.

While it may seem as if you’re allergic to your AC, you’re most likely just having a reaction to air contaminants being circulated by the unit. There are a number of possible things that can cause airborne contaminants in your home, but there are also ways to minimize these allergens.

In rare cases, a reaction to air conditioning can be from a condition known as cold urticaria. If you suspect you may have this condition, talk to your doctor.