Types of Mold: 12 Common Household Molds and How to Identify Them

Why Mold Type Matters

Different mold species produce different levels of toxins. Knowing your mold type determines how urgently you need to act, whether you can DIY the cleanup or need a professional, and whether the mold is contributing to health symptoms.

Low risk molds like Cladosporium and Alternaria are extremely common and cause mild allergic reactions in sensitive people. They grow on almost any damp surface and are found both indoors and outdoors. Cleaning them with Concrobium or hydrogen peroxide is usually sufficient.

Moderate risk molds like Penicillium and common Aspergillus species produce some mycotoxins and can cause significant allergic reactions and respiratory irritation. They need attention but do not usually require emergency remediation.

High risk molds like Stachybotrys, Chaetomium, and Aspergillus fumigatus produce potent mycotoxins or can cause invasive infections. These require professional remediation with containment, HEPA filtration, and post-clearance testing.

The EPA does not distinguish between mold types in its remediation guidelines because the cleanup process is similar regardless of species. However, knowing the type helps you understand the health risk and urgency.

Black Molds

Stachybotrys chartarum (Toxic Black Mold)

Appearance: Dark greenish-black, slimy when wet, powdery when dry. Grows in thick patches on cellulose materials.

Where it grows: Water-damaged drywall, ceiling tiles, cardboard, and wood. Requires constant moisture for at least 72 hours to establish. Found behind walls with slow leaks, in flood-damaged basements, and on chronically wet ceiling tiles.

Health risk: HIGH. Produces trichothecene mycotoxins and satratoxins. Linked to CIRS, respiratory damage, neurological symptoms, and immune suppression. The most feared household mold.

Action: Do not disturb. Professional remediation with containment required for areas larger than 10 square feet. ERMI testing recommended.

Cladosporium

Appearance: Dark green to black, suede-like or powdery texture. Forms in circular patches.

Where it grows: Window sills, bathrooms, textiles, carpets, under sinks. One of the most common indoor molds. Also extremely common outdoors.

Health risk: LOW. Causes mild allergic reactions (sneezing, runny nose) in sensitive individuals. Does not produce significant mycotoxins. Rarely causes serious illness except in severely immunocompromised people.

Action: Clean with standard mold cleaning products. Fix moisture source. No professional needed for small areas.

Aspergillus niger

Appearance: Black with a white or yellow border. Powdery texture. Grows in dense circular colonies.

Where it grows: Damp walls, decaying vegetation, HVAC systems, and stored food. Very common in homes with humidity issues.

Health risk: MODERATE. Can cause aspergillosis (lung infection) in immunocompromised people. Produces ochratoxin A. Most healthy people tolerate low exposure without symptoms.

Green Molds

Penicillium

Appearance: Blue-green to teal, velvety or powdery. Spreads rapidly in concentric rings.

Where it grows: Water-damaged wallpaper, carpet, insulation, mattresses, upholstered furniture, and stored food. One of the fastest-spreading indoor molds.

Health risk: MODERATE. Major allergen. Some species produce penicillic acid and other mycotoxins. Chronic exposure linked to sinus infections and respiratory inflammation.

Aspergillus (green species)

Appearance: Green, yellow-green, or gray-green. Powdery. Over 180 species exist, and several are green.

Where it grows: Nearly anywhere with moisture: walls, ceilings, HVAC systems, food, soil, and insulation. The most common mold genus found in indoor environments.

Health risk: MODERATE to HIGH depending on species. A. fumigatus is the most dangerous (invasive aspergillosis). A. flavus produces aflatoxins (potent carcinogens). A. versicolor produces sterigmatocystin. Many species produce allergens.

Trichoderma

Appearance: White to bright green, cottony or woolly texture.

Where it grows: Damp drywall, wallpaper, wet carpet, and HVAC filters. Grows rapidly on cellulose in high humidity.

Health risk: MODERATE. Produces enzymes that destroy building materials. Some species produce trichothecene mycotoxins (the same class as Stachybotrys). Causes allergic reactions and respiratory irritation.

White Molds

White mold is tricky because it is often confused with efflorescence (mineral deposits from water evaporation on concrete). Efflorescence dissolves in water. Mold does not.

Early-stage Penicillium and Aspergillus

Many molds start white before developing their characteristic color. Young Penicillium colonies are white before turning blue-green. Young Aspergillus colonies are white before turning green, black, or yellow. If you see white fuzzy growth on a damp surface, it is almost certainly mold in an early stage.

Sclerotinia

Appearance: White, cottony. Often found on stored food and in crawl spaces.

Where it grows: Organic materials in damp, cool environments. Common in crawl spaces, basements, and on stored produce.

Health risk: LOW. Primarily a plant pathogen. Minimal direct health risk to humans but indicates high moisture conditions where other molds will follow.

Pink, Orange, and Yellow Molds

Serratia marcescens (Pink "Mold")

Appearance: Pink to reddish-orange, slimy film. Not actually a mold. Serratia is a bacterium.

Where it grows: Shower tiles, toilet bowls, sinks, pet water bowls. Anywhere with standing water and soap residue.

Health risk: LOW to MODERATE. Can cause urinary tract infections if it enters the body. Generally harmless on surfaces. Clean with hydrogen peroxide or bathroom cleaner.

Aureobasidium (Pink-Black Mold)

Appearance: Starts pink, turns dark brown to black as it ages. Slimy.

Where it grows: Window frames, caulk, wooden surfaces, painted walls. Common in bathrooms and kitchens.

Health risk: MODERATE. Causes allergic reactions. Can cause skin infections on direct contact. Wear gloves when cleaning.

Fuligo septica (Yellow "Dog Vomit" Mold)

Appearance: Bright yellow, spongy, looks like scrambled eggs. Actually a slime mold, not a true mold.

Where it grows: Mulch, lawns, garden beds. Occasionally found on basement walls near garden entrances.

Health risk: VERY LOW. Not toxic. Harmless but alarming in appearance. It disappears on its own within days.

How to Identify Your Mold Type

You cannot reliably identify mold species by looking at it. Many species look identical to the naked eye. Here are your options from quickest to most accurate:

Visual clues (rough guide only): Color, texture, location, and growth pattern give you a starting point but are not definitive. Use our Mold Scanner AI app to compare your mold against known species photos.

Surface tape lift test ($30 to $50): Press clear tape on the mold, seal in a container, and mail to a lab. Results in 3 to 5 days. Identifies the genus (Aspergillus, Penicillium, Stachybotrys) growing on that specific spot.

ERMI dust test ($200 to $400): Vacuums dust and uses DNA analysis to identify all 36 mold species in your home environment. The gold standard for comprehensive identification.

Professional inspection ($300 to $700): Combines air sampling, surface sampling, and visual expertise. The inspector identifies species and quantifies your exposure level.