“Black mold” and “toxic mold” are not medical terms and don’t mean the mold is more dangerous.

Molds are a normal part of our environments.

Indoor water problems and excess moisture can cause mold overgrowth, causing symptoms in some people.

To fix the mold problem, fix the water or moisture problem.

Mold is a type of fungus. It is common in our outdoor environments and grows in damp places (such as near lakes or forests). Mold reproduces through spores. Mold can grow in the home when there is water damage, excess moisture, or high humidity. Signs of mold are usually a musty smell and/or discolored spots on walls, furniture, and carpet.

There are hundreds of species of mold, including Aspergillus, Penicillium, Alternaria, and Cladosporium, and Stachybotrys. Under certain environmental conditions, Stachybotrys and other molds can produce toxic substances called mycotoxins. The main way people are exposed to mycotoxins is through food. Mycotoxins can be found primarily on grain and nut crops but also on other fruit & vegetable produce. The United States has strict regulations and monitoring to minimize this exposure through food.

Mycotoxins do not release into the air, they tend to “stick” to the mold. Therefore they are unlikely to pose a risk to people who live in a home with mold. Stachybotrys is commonly referred to as “black” or “toxic” mold and can cause great concern to families given its media coverage. However, Stachybotrys is no more harmful than other types of mold. Many different species of mold can be black or produce mycotoxins under specific conditions.

In general, all molds in the home should be treated the same. This means remediation (cleaning up the mold and fixing the underlying excess water issue).

Mold exposure can affect people differently. The most common health effects from exposure to mold are allergies (hay fever), and asthma.

For individuals who are generally healthy, symptoms caused by exposure to mold can include sneezing, runny nose, cough, and itchiness of the eyes/nose. There is some evidence that living around mold when young can increase the risk of developing asthma.

Some people who are more vulnerable include people with allergies, asthma, lung problems, or conditions that make their immune system weaker (“immunocompromised”). Immunocompromising conditions include cancer, transplants, HIV, or other medications that affect the immune system. In those who are immunocompromised, mold can cause infections of the skin or other organs. Additionally, mold can affect the health of farm workers when they work frequently with large amounts of moldy hay or moldy food.

Mycotoxins can be harmful to people who eat them in high amounts. This typically happens from contaminated food in countries without testing of produce. This is unlikely in the United States because the Food and Drug Administration monitors mycotoxins in our food supply. Very low levels, or trace amounts, can be found in some common food products like grains and nuts.

There is currently no scientifically researched evidence to link mold exposure to conditions such as autism, Parkinson’s, autoimmune disorders, or memory issues.

Some patients (especially those with asthma or allergies) may benefit from environmental allergy tests to understand whether their symptoms could be triggered by mold. However, there are no doctor-recommended tests to measure the amount of mold or mycotoxins in the body.

If you are concerned about allergies or asthma in your child, these concerns should be discussed with your child’s pediatrician. The doctor may perform environmental allergy testing or refer your family to an allergist (a doctor who specializes in allergies). This testing may include skin or blood tests. It is helpful to test for multiple allergies because children may be allergic to other allergens in their environment. Other allergens include dust mites, cockroaches, or other pests.

There are many other mold and mycotoxin tests advertised, such as tests for mycotoxins in the urine. These tests are not ordered by your doctor and they can be a large out of pocket expense. Currently, these tests are not recommended, including by the Centers for Disease Control and Prevention. One of the main reasons is that they are not clinically validated. This means that we do not know enough about these tests yet to determine what they do and do not mean for your child’s health. They do not give useful information about your child’s previous exposures to mold or how to manage your child’s symptoms.

If your child has allergies or asthma, your child’s doctor can recommend treatment for the allergies or asthma. Aside from treating allergy and asthma symptoms, the most important treatment for mold is removing the exposure. This includes finding the source of the water, stopping that source (if it comes from a leak), and cleaning up the mold.  Other advertised treatments for mold exposure, including alternative medicines and detoxification programs, should be avoided. These treatments currently are not scientifically proven and can be harmful to your child.  

Home testing is generally not needed and can be costly. Signs of mold (water damage, musty smells, or mold spots) are enough evidence to take action. Mold testing can only tell you if the levels inside your home are more than typical outdoor levels. There are no current guidelines for acceptable levels of mold or mold spores in the environment.

It can be helpful to hire a professional to look for sources of water damage or water leaks and mold growth. These experts can also assist with a plan to fix these issues.

  1. Identify and fix the source of water damage (or humidity/dampness) that led to the mold growth.
  2. Safely remediate the mold growth.

It can be helpful to hire a professional to look for sources of water damage, water leaks, or mold growth. 

If the mold is in a small area (around less than 10 square feet), families can usually clean up the mold. We recommend soap and water. We do not recommend bleach, unless disinfection is needed (for example, if you are cleaning water damage from a sewage leak). In this case, use no more than 1 cup of bleach mixed in 1 gallon of water. Bleach can be a strong irritant. Never mix bleach with ammonia, as they can combine to create a deadly gas. It is important to fully dry the area once cleaned. We recommend using proper gloves, eye and respiratory protection. You should make every effort to avoid the spread of mold. Children and/or those with underlying breathing issues should not be present when the cleaning is taking place. 

If it is a larger area (more than 10 square feet, multiple rooms, multiple walls), it is best for an expert to perform the cleanup and repairs. Financial or legal resources may be available for this process depending on where you live and if you own or rent your home. 

Older homes with water damage are likely to have other possible risks such as lead paint, dust mites, or pests. If there is lead-based paint in your building, any remediation work should be done by a “Lead Safe Certified” contractor.  

See the side panel for resources and laws and regulations based on your location. 

To prevent future mold growth, it is important to identify the underlying conditions causing mold. Typically, this means fixing leaks and taking steps to reduce excessive moisture. It is good to look around your home routinely to check for issues. Issues include water leaks, high humidity, water leak spots, areas of dampness, musty smells or mold growth. Fixing these issues early can avoid larger problems. 

Other helpful tips to improve the air quality in your home are: 

  • Open windows to help circulate air and ventilate your home 
  • Open windows and/or use bathroom exhaust fans if available when showering to avoid high humidity 
  • Use an exhaust fan when cooking  
  • Consider using a dehumidifier  
  • Perform wet mopping and dusting regularly   

Updated: Hannah Thompson, MD MPH and Emma Holland, RN MPH; April 2024