Like pollen, mold can produce tiny particles that can pass right through the respiratory tract and into the bloodstream.
If you have recently experienced water damage, you may have mold or harmful microbial particles circulating in the air in your home. For many people, exposure to these things can result reaction like an allergy. That is why it is important to take care of the damage of the water.
If you are damaged by water, I advise you to call your insurance company immediately if you have one, (as it can be covered by insurance) and make sure someone is there within 24 hours to remove wet building materials. Some molds can grow as fast as 24 hours. Once wet building material has been removed, it is important to make sure the surrounding area is always dry. I recommend dehumidifying the air transducers (another is water damage), as the air transducers can inadvertently blow mold and / or surrounding toxins.
If you think the water may have been in for longer than 24 hours, then you will want to hire a professional mold treatment company to remove the building material according to the right engineering controls (with equipment personal protection, plastic box and air purifier). The fastest possible response is the best way to make sure that the problem does not get worse and cause adverse health reactions by not drying the space properly within the first 24 hours.
Cleaning with a single towel is not enough as water can be trapped between building substrates for a longer time, even if the surface is already dry. (Think what will happen if you leave a wet towel on the floor. The floor underneath the towel will be wet for a long time because it holds moisture between the floor and the towel. This is what happens between your wall and floor. when there is a significant leak.)