They are neither plant nor animal. They grow – and live on – the dead. No, they are not zombies, but rather, mold, a diverse group of microorganisms in the kingdom fungi.
Despite their dastardly rap, mold organisms are not all bad. By decomposing organic matter, they help perform recycling for the ecosystem. "Mold are responsible for the breakdown of dead organic material, whether plant or animal," says Dr. Matthew J. Kates, chief of the Division of Otolaryngology-Head and Neck Surgery at Sound Shore Medical Center in New Rochelle, NY. "Mold reproduce and spread in the environment by releasing tiny particles called spores." Spores, he says, are what people inhale in and react to. "They grow best in moist areas and cause most allergic symptoms in the summer when it is warm and damp."
These microscopic spores find a wet or moist areas in which to grow. Unchecked, growth – which is fueled by dead organic material, plus moisture and air -- will spread to neighboring habitable materials. Mold will grow on rotting wood, grass and compost piles. But molds also thrive in bathrooms, basements, carpeting and wood inside the walls. And, says Dr. Kates, as in the case with other allergies, a person with a sensitive immune system and a genetic predisposition to allergies can develop mold allergies with enough repeated exposure.
"There are many different types of mold but only a few cause allergic reactions," says Dr. Kates, "Some common molds are Alternaria, Aspergillus and Penicillium." Fungi, he says, can harm the body more through infection than they do through the allergic pathways. But in the sinuses, fungi can cause allergic fungal sinusitis.
Molds are also hardworking, and, unlike pollen, they don't take the winter off. "Mold allergies can appear in the warm, humid summer months, or even year 'round," says Dr. Kates. Some people are allergic to different kinds of mold, but regardless, the manifestations of the allergy are similar. "Mold allergies can produce the same symptoms that pollen and animal dander do." These symptoms, says Dr. Kates, include nasal congestion, itchy, runny eyes and sneezing. And for people suffering with asthma, mold allergies can even cause wheezing. Dr. Kates recommends blood testing to "characterize the exact substance to which one is allergic."
Although mold spores are originally invisible to the human eye, when molds start growing they usually become easy to spot if you know what you're looking for. Molds can appear as discoloration in black, green, gray, brown and other colors. But they might not be noticeable until structural damage has occurred in the home or health problems have been noticed.
What should you do when you've detected mold – and have developed an intolerance for them? Dr. Kates recommends avoiding or limiting exposure. "If there's no mold in your home, stay indoors when mold counts are high," he says. He also recommends fixing leaks in the home and dehumidifying the basement, where mold often thrives rampantly.
The next step, he says, is to consider speaking to a medical professional about taking medications, such as "antihistamines, antileukotrienes, decongestants and/or steroids, either inhaled or by mouth." The third course of treatment, says Dr. Kates, might be immunotherapy -- allergy shots -- wherein an increasing dose of the allergen helps the body to desensitize and to not react to the real thing, mold, in the environment.
Or, you can always consider moving to Arizona. Then again, you'll have to worry about sunscreen.