Is Black Mold Dangerous? What the Evidence Really Shows

"Black mold" is the name the news media often use for Stachybotrys chartarum. But the EPA says "black mold" is not a species or specific kind of mold, and neither is "toxic mold", so color alone doesn't tell you what you have.

The CDC says it is not necessary to determine what type of mold you may have growing in your home. Whatever the color, the response is the same: remove it and fix the moisture. For identification and cleanup, see our black mold guide.

Yes, in the sense that any indoor mold can harm some people. No, in the sense that it's not uniquely deadly.

The CDC says exposure to damp and moldy environments may cause a variety of health effects, or none at all. Cleveland Clinic says black mold rarely causes serious illness, though it may make asthma worse.

The people who should take any mold most seriously, per the CDC:

• People with asthma or mold allergies, who may have severe reactions.
• People with weakened immune systems or chronic lung disease, who may get infections in their lungs from mold.

For these groups, the CDC says immune-compromised people should not stay in a moldy home, or even be there while it is being cleaned.

Black mold does what other indoor molds do. The documented effects are mostly in the nose, eyes and lungs.

Table: what black mold does to you, by type of effect.

Cleveland Clinic adds that chronic fatigue, brain fog, headache and widespread body or joint pain are not typical symptoms of black mold exposure. If you have them, see a doctor; they may have another cause that needs treatment. For the full symptom picture, see black mold symptoms.

Interestingly, Stachybotrys isn't a big allergy trigger. The American Academy of Allergy, Asthma & Immunology (AAAAI) position paper on mold said Stachybotrys is unlikely to be a relevant clinical allergen in human subjects because it is poorly aerosolized.

Some molds, including Stachybotrys, can make chemicals called mycotoxins. That's where the "poison" idea comes from. Here's what's known:

• Mycotoxins in food are a real hazard. The NIEHS says some molds produce mycotoxins, which are substances that can cause severe illness if ingested. The AAAAI paper notes that eating large doses from spoiled or contaminated food can cause severe human illness.
• Mold doesn't always make toxins. The same paper says the mere presence of such a mold should not be taken as evidence that the mold was producing any mycotoxin.
• Breathing them at home is a different matter. The AAAAI paper concluded that toxicity from inhaled mycotoxins in nonoccupational settings is not supported by the current data, and its occurrence is improbable. Cleveland Clinic says there's no scientific proof that mold toxins cause conditions that affect your whole body.
• Science isn't finished. The EPA says some mycotoxins are known to affect people, but for many, little health information is available. The NIEHS describes ongoing research suggesting long-term exposure to inhaled mycotoxins may promote inflammation and immune system changes.

The AAAAI 2006 paper is two decades old, so it's fair to ask whether the view has changed. The AAAAI's 2026 patient page still says reviews by the Institute of Medicine and the World Health Organization found the available evidence was insufficient to support a relationship between mycotoxin inhalation and the nonspecific symptoms often blamed on mold.

So "black mold poison" overstates what's known. Mold in your home is a health concern worth fixing, not a poisoning.

The idea that black mold kills came largely from a cluster of infant lung bleeding cases in Cleveland, Ohio, in the 1990s.

What happened. A CDC report described 10 infants with acute idiopathic pulmonary hemorrhage (sudden bleeding in the lungs) who had one or more bleeding episodes, resulting in one death, between January 1993 and December 1994. Early study results linked the cases to major household water damage during the 6 months before illness and to higher levels of household fungi, including Stachybotrys.

What the CDC found when it looked again. The CDC convened a multidisciplinary internal group of senior scientists and asked outside experts to review the work. Their review, published in Morbidity and Mortality Weekly Report, found problems:

• The statistical estimate linking the mold to the illness was very sensitive to at least three influential steps or strategies in the analysis.
• Among water-damaged homes, culturable Stachybotrys was found in similar proportions of case and control homes.
• The methods did not distinguish between contamination and clinically meaningful exposure.

The conclusion: The associations should be considered not proven; the etiology of AIPH is unresolved.

Later reviews agreed. The Institute of Medicine's 2004 report placed acute idiopathic pulmonary hemorrhage in infants in its "inadequate or insufficient evidence" category. The CDC's current Stachybotrys page says a possible link has not been proven. The AAAAI says there was insufficient evidence of a relationship between bleeding in the lungs in infants and Stachybotrys exposure.

"Not proven" isn't the same as "proven safe." The CDC still says parents should make sure children get proper medical treatment, and a moldy home with a baby in it should be fixed promptly.

We found no CDC, NIH or allergy-society source stating that black mold in a home has been shown to kill healthy people. The one famous case cluster, in Cleveland, was judged not proven.

Where mold can be life-threatening is fungal infection in people with seriously weakened immune systems, and that's usually a different mold. The CDC says aspergillosis, caused by the common mold Aspergillus, can cause mild to severe illness, and people with weakened immune systems or lung diseases are most at risk. The most serious form, invasive aspergillosis, is uncommon and occurs primarily in immunocompromised people, such as people with blood cancers or transplants. Our guide to mold and your lungs explains this.

If someone in your home is immune-compromised, treat any mold seriously, keep them out during cleanup, and talk to their doctor.

See a doctor if symptoms last or keep returning. The CDC says individuals with persistent symptoms should see their physician. A doctor, not a mold test, decides whether mold is affecting your health. The CDC says no test exists that proves an association between Stachybotrys chartarum and particular health symptoms, and urine "mycotoxin" tests are not approved by FDA for accuracy or for clinical use. See our guide to mold exposure tests.

For emergencies, Cleveland Clinic says to go to the nearest emergency room as soon as you can if you have trouble breathing.

The CDC is clear: if Stachybotrys chartarum or other molds are found in a building they should be removed. You don't need to test to identify the species first.

1. Find and fix the water. Mold follows moisture: leaks, flooding, condensation. In Texas, flood-damaged homes need fast action; see mold after a flood.
2. Small patches: TDLR says areas of visible mold of less than 25 contiguous square feet can be cleaned up by people who are not licensed. Wear at least a NIOSH Approved N95 respirator, gloves and goggles. Our vinegar vs bleach guide covers cleaners.
3. Larger or hidden mold: Hire a licensed mold testing company to assess and write a plan, and a separate licensed mold removal company to do the work. Texas law says a license holder may not perform both mold assessment and mold remediation on the same project.

Find licensed pros in Houston, San Antonio, Dallas or Corpus Christi, or browse the Texas directory. Check any license with our license check tool and see how we verify. For costs, see mold remediation cost.