A single mold spore is a tiny, microscopic little thing that usually thrives in damp places. Yet for its diminutiveness in size, mold spores can be deadly to people who have allergic reactions to them.

Most allergies start with airborne allergens. And while mold spores often stick to walls and surfaces, because they are so tiny, they can easily float in the air when disturbed. A person with mold allergies can easily breathe these mold spores, permitting them to pass through the nasal passages and to the lungs, triggering an allergic reaction.

Mold allergies are even more common than pollen allergies. That’s because pollen allergies are often seasonal, like ragweed during the fall, grass pollen in the spring, and cedar fever in December or January. With mold allergies, however, it’s different. Molds can affect you at night, with little regard to seasons. And while pollens are released during the day when sunlight dries the pollen and the wind picks them up and spreads them around, mold cannot tolerate sunlight and hence only goes off during the night. The process is called “sporulation,” which is different from pollen’s pollination.

The highest mold counts occur in our homes around 2:00 a.m. because that’s the time when spores blow out of our air-conditioning systems and spread throughout the house. The first thing that happens during the onset of mold allergies is swelling in the mucus membrane. This is then followed by the release of adrenaline, your emergency allergy hormone. The release of adrenaline is also the reason why you suddenly find yourself waking up in the wee hours of the morning and wondering why you can’t breathe through one nostril.

To control allergic reaction to molds, the first step is to recognize the triggers. Because once you do, you’ll at least know when to avoid them. You can also have an allergist test you for positive response to mold. However, the problem with this is that there are far too many species and mutant varieties of molds that it’s difficult to test you for every single one of them. One thing you should know if you have mold allergies is that molds need a place to grown on and a source of nutrients. Damp places are their personal favorites, but the dust in your air conditioning system may also provide them with nutrients to support them.

Here are common places where mold colonies may thrive:

Another place where molds may grow is your car. Researchers have noticed that many people suffered mold allergies in their cars with symptoms like sinus problems, asthma, drippy nose, and headaches. The cause of this was attributed to leaky windows or doors, often the result of aged weather stripping. This causes water to leak in and wet the carpet of upholstery, contributing to mold growth.