All mold allergies are the result of your body's misidentification of mold spores, which are the little seeds that mold releases in order to reproduce. Your immune system thinks they're dangerous, even though they're really harmless. Once your body makes the mistake the first time, it will keep making it from then on. There are many types of mold, but allergies are most commonly caused by a select few. Some of the types of mold that cause allergies are: alternaria, cladosporium, aspergillus, penicillium, helmin thosporium, epicoccum, fusarium, mucor, rhizopus and aureobasidium. Since fungi tend to be significantly different from one another, chances are that just because you're allergic to one type of mold doesn't mean you'll be allergic to another.
While molds tend to reproduce in the hot months of the summer, there are enough types of molds and enough places they can grow that some people can end up suffering from mold allergies year-round. Outdoors, mold often collects in moist places; rotting logs and piles of leaves are common mold havens. These outdoor types of mold don't usually cause allergies during the winter. However, indoor molds can cause trouble anytime since they tend to grow in places like the bathroom, kitchen and basement, which remain damp consistently. The soil in house plants can harbor mold too, but it doesn't usually pose a problem unless you stir up the dirt.
People who are exposed to mold because of their line of work are more at risk for mold allergies. Such occupations include farming, logging, baking, working in a greenhouse, fixing or building furniture and making wine. Even though mold is present in many types of food -- thanks to mushrooms, yeast, vinegar and soy sauce -- edible fungi aren't thought to trigger mold allergies.