Hello Adiya! Thank you for asking at HealthReplies.com.
In general, an air conditioner (AC) does not contain harmful substances. A good air conditioner has a filter in it which is actually very good at filtering indoor air, so that the air becomes cleaner and healthier. However, if not cleaned and cared for properly, air conditioning can store dust and various germs that are harmful to health, especially the health of our airways. Normal people may not have major problems due to this, but people with asthma or sensitive allergies can have dangerous attacks. Therefore, the filter in the air conditioner must be cleaned regularly according to the instructions for use when you first bought the air conditioner. If you or someone close to you is still bothered (has a cough, sneeze, or has an attack) when you are in a clean, air-conditioned room, you can add an air purifier.
AC is very useful for dealing with temperatures that are too high. In areas with high temperatures, using air conditioning can prevent you from heat stroke and other heat-related illnesses. A temperature difference that is too far between outdoors and indoors will not cause problems for normal people, but can cause a mild cold in people with allergic rhinitis or sinusitis. Air conditioning also makes humidity lower, so that germs in the room are not easy to grow. However, it can also make your skin drier in an air-conditioned room. Make sure you always drink enough water. You can also use a moisturizer if necessary.
That's my explanation. I hope this helps.