Black mold: what it is, whether it's dangerous, and what to do

What is black mold?

“Black mold” is a nickname, not a scientific category. Most people who use it mean Stachybotrys chartarum, which CDC describes as a greenish-black mold that grows on materials high in cellulose, such as fiberboard, gypsum board (drywall) and paper. CDC says it needs constant moisture to grow, which is why it shows up after water damage, slow leaks, condensation or flooding rather than on a surface that gets damp now and then. You can read a short definition in our Stachybotrys glossary entry.

The catch is that many molds are dark. CDC lists Cladosporium, Penicillium and Aspergillus as the most common indoor molds, and says mold “can look like spots of many different colors.” EPA’s mold guide makes the same point: molds come in many colors, including both white and black. So a black patch on your wall could be Stachybotrys, or it could be one of several ordinary household molds. Color alone cannot tell you which one, and as the sections below explain, the answer does not change what you should do. For the bigger picture on identification, cleanup and costs, start at our mold hub.

What does black mold look like, and what else could it be?

Black mold shows up as dark patches on drywall, ceiling board or wood that stayed wet. Other molds, and some things that are not mold, look similar. The table sorts out common look-alikes.

EPA says a musty odor suggests mold growth worth investigating. See signs of mold in a house.

Is black mold more dangerous than other mold?

The major health agencies say no. CDC’s Stachybotrys fact sheet states that it is “not necessary to determine what type of mold you may have,” and that all molds “should be treated the same with respect to potential health risks and removal.” CDC also says that no test exists that proves an association between Stachybotrys and particular health symptoms.

Stachybotrys can produce mycotoxins, and that fact drives much of the fear. But the American College of Medical Toxicology (ACMT), in its 2025 position statement, stresses that finding a toxin-producing mold does not mean toxins are present, or present at doses that matter. ACMT says indoor airborne mycotoxin levels are “exceedingly low” and that the available evidence gives no compelling data that inhaled mycotoxins pose significant health risks in homes, schools or offices.

The American Academy of Allergy, Asthma & Immunology (AAAAI), in its July 2026 review, reaches the same place: both the Institute of Medicine and the World Health Organization concluded the evidence was insufficient to tie inhaled mycotoxins to the wide range of nonspecific symptoms sometimes called “toxic mold syndrome.” That does not make Stachybotrys harmless. It means it carries the same kinds of risks as other indoor molds, and it should be removed the same way.

Where did the black mold scare come from?

Much of it traces to a cluster of infant deaths from bleeding in the lungs in Cleveland, Ohio, in 1993 and 1994. AAAAI’s history of the episode explains that CDC researchers initially reported that affected infants were more likely to live in homes with detectable Stachybotrys. After a second report in 1997, CDC ran internal and outside reviews. In March 2000, CDC published an update concluding that, because of shortcomings in how the investigation was carried out and reported, a possible association between the infant lung bleeding and Stachybotrys “was not proven.” AAAAI notes that other exposures in the homes, such as tobacco smoke, may have contributed.

By then, AAAAI says, media coverage and a series of multimillion-dollar lawsuits had made the “toxic” label a household phrase. The Institute of Medicine’s 2004 review, Damp Indoor Spaces and Health, later placed acute idiopathic pulmonary hemorrhage in infants in its lowest evidence tier: inadequate or insufficient evidence to say whether any association exists. CDC’s current fact sheet still says the possible link “has not been proven.” We cover the full evidence picture on our mold symptoms page.

What health effects can indoor mold actually cause?

CDC says exposure to damp and moldy environments “may cause a variety of health effects, or none at all.” The effects with the strongest support are respiratory and allergic. According to CDC, mold can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes or skin rash in some people. People with asthma or a mold allergy may have severe reactions. People with weakened immune systems or chronic lung disease can get lung infections from mold.

EPA describes the same set: allergic reactions that can be immediate or delayed, asthma attacks in people with asthma who are allergic to mold, and irritation of the eyes, skin, nose, throat and lungs in both allergic and non-allergic people. EPA adds that symptoms other than allergic and irritant types “are not commonly reported” from inhaling mold.

The 2004 Institute of Medicine review found sufficient evidence of an association between indoor mold and upper respiratory symptoms, cough, wheeze, asthma symptoms in sensitized people, and hypersensitivity pneumonitis in susceptible people. Fatigue, memory problems and other neuropsychiatric symptoms were in the inadequate-evidence tier, so they are not supported by current evidence. If you have allergy-type symptoms at home, our mold allergy guide explains how allergists test for it.

Should you test the mold to find out if it is black mold?

No. CDC does not recommend mold testing. Its reasons: health effects differ from person to person, so sampling cannot tell you whether someone will get sick; there are no set standards for an acceptable amount of mold in a home; and testing can be expensive. EPA adds that “if visible mold growth is present, sampling is unnecessary,” and that there are no EPA or other federal limits for mold or spores to compare results against.

Paying to learn the species does not change the plan. CDC’s Stachybotrys guidance is that if it or any other mold is found, it should be removed. The money is usually better spent fixing the water problem.

Testing by a qualified professional can still have a role in specific situations, such as tracking down hidden mold, documenting conditions for a dispute or insurance claim, or confirming that a professional cleanup worked. EPA says surface sampling may help show whether an area was adequately cleaned, and that sampling should be designed and interpreted by professionals with specific experience. Our page on home mold test kits explains when a test is worth it and when it is not. For health testing, see our page on mycotoxin urine tests, which major medical groups say are not validated.

How do you get rid of black mold?

You remove Stachybotrys exactly the way you remove any other mold. EPA’s rule of thumb: if the moldy area is less than about 10 square feet, roughly a 3 ft by 3 ft patch, you can usually handle it yourself. Larger areas, contaminated HVAC systems and damage from sewage or other contaminated water call for a professional.

The core steps from EPA and CDC:

1. Fix the leak or moisture source first. EPA says that if you clean the mold but do not fix the water problem, it will most likely come back.
2. Protect yourself with at least an N95 respirator, gloves and goggles, as CDC recommends. Our mold cleanup PPE checklist covers fit and options.
3. Scrub hard surfaces with detergent and water, then dry completely. EPA does not recommend bleach as a routine practice. If you do use it, CDC says use no more than 1 cup of household bleach per gallon of water and never mix it with ammonia.
4. Throw away porous materials like ceiling tiles and carpet that have become moldy. EPA says mold can fill the crevices in porous materials, so it may be impossible to remove completely.
5. Dry wet materials within 24 to 48 hours to prevent regrowth (EPA).

Our step-by-step guide on how to get rid of mold yourself goes deeper, and what actually kills mold compares cleaners.

Do you need a licensed mold pro for black mold in Florida?

Florida is one of the few states that licenses mold work. Under Florida Statutes section 468.8411, “mold assessment” and “mold remediation” are defined as work on mold growth of greater than 10 square feet. Below that size, the state’s mold licensing definitions do not apply, which lines up with EPA’s 10-square-foot DIY guideline.

Florida law also separates the person who inspects from the person who removes. Section 468.8419 bars a mold assessor, or the assessor’s company, from performing remediation on a structure it assessed within the previous 12 months, with a narrow exception for certain Division I contractors. The same section prohibits assessors from taking referral payments from remediators. The point of the rule is that the company diagnosing the problem should not profit from the size of the fix.

If you hire help in Florida for a large patch, ask for the license number and check it with the Florida Department of Business and Professional Regulation. Our mold licensing by state guide covers Florida, Texas, New York and Louisiana, and our guide to choosing a mold remediation company lists the questions to ask. For what a professional job typically costs, see our mold remediation cost guide.