Mold is a type of fungus that grows both indoors and outdoors and thrives on moisture. Mold sprouts from tiny spores that float about in the air and settle on moist surfaces, where they reproduce into mold colonies. There are thousands of types of molds all over the world, most of them harmless. But some mold becomes a problem when it impacts the integrity of your home.

Some molds are also toxic and may affect your health. If mold is present in your home, you might begin to notice a damp, musty odor in a specific area. It’s commonly found in bathrooms, basements and kitchens. If you notice a musty odor, you should check for damp walls, carpet, flooring and any other spaces that may be breeding grounds for mold. The key is to treat a mold problem immediately, before the infestation becomes worse or causes permanent damage.

Types of Mold Mold comes in a variety of hues, including black, white, green and orange. The most common types of mold include aspergillus, cladosporium and stachybotrys chartarum (also known as black mold). Aspergillus is a fairly allergenic mold that is commonly found on foods and in-home air-conditioning systems. Cladosporium is typically a black or green “pepper like” substance that grows on the back of toilets, painted surfaces and fiberglass air ducts. While this mold is nontoxic to humans, it can trigger common allergy symptoms such as red and watery eyes, rashes and a sore throat.

Mold that appears to be orange or red in color is typically found outdoors, given its nature to thrive on decaying plants or moist wood. This type of mold, which can appear slimy, is harmless and should only be removed for aesthetic purposes.

White mold is not technically a type of mold, but the good news is that this typically indicates the mold is only in the early stages of growth and can easily be treated.

Mold vs. Mildew Homeowners often refer to mold and mildew interchangeably, but it’s important to distinguish mildew from mold. Mildew is a common type of mold that sits on the surface of damp walls, doors, shower grouting and more. This type of mold looks like tiny black spots that have a flat, sometimes powdery appearance. Mold is a broader term that refers to many mold species. It can be green, black or red, and often feels slimy. “Mold is typically more serious and costly to remediate than mildew,” says Jennifer Rodriguez, chief hygiene officer for Pro Housekeepers. Whereas mildew can easily be scrubbed away with a cleaning brush and store-bought mold killer, mold is often more stubborn and may require extra steps or professional remediation to remove.

How to Identify Mold and Mildew Learning how to distinguish between mold and mildew is important, even if you inadvertently use the terms interchangeably.

Mildew is a specific type of mold that develops on the surface of damp walls, doors, shower grouting and similar areas. It appears as small, flat black spots and occasionally has a powdery texture.

The term mold is broader as it is intended to encompass multiple mold species. Homeowners might find it manifesting in a range of colors such as green, black and even red. Unlike mildew, mold might have a slimy texture. A surface cleaning isn’t usually enough to combat mold spores.

While mildew can be easily scrubbed away using a cleaning brush and store-bought mold killer, different types of mold are usually more resistant to cleaning products. Mold spores can take hold and spread and require homeowners to take on additional cleaning efforts or seek professional mold remediation for complete removal.

What Does Black Mold Look Like?

Common black mold (Cladosporium) presents as small black spots in ordinary spaces. It can grow inside and outside of the home, and it’s far less harmful than toxic black mold. Non-toxic black mold is easier to clean and less musty, but it can still trigger allergic reactions in people with sensitivities.

The black mold you’ll mostly hear talked about is (Stachybotrys chartarum), which can make you sick if you have mold allergies. If you have a weakened (compromised) immune system, it can cause fungal infections in your airways or other parts of your body.