Alternaria is one of the types of mold that commonly causes allergic reactions. If you're allergic to mold and you breathe in alternaria spores, chances are that your immune system will go haywire. Your body thinks that alternaria is extremely dangerous, even though it isn't, and antibodies are released. The antibodies trigger chemicals like histamine that bring on the allergic symptoms you might be familiar with.
Such symptoms are typically the same among all types of hay fever: sneezing, itchy and watery eyes, runny nose, congestion, coughing and dry skin. These symptoms can set in almost immediately after you breathe in alternaria spores, or they may take a little longer to show up. Each time you're exposed to alternaria, your immune system will react -- most likely with increasing intensity. Other types of mold that are likely to cause the same reactions as alternaria are cladosporium, aspergillus, penicillum, fusarium and rhizopus.