Mold Allergy: Symptoms, Causes, Types, and Treatment

Mold Allergy: Symptoms, Causes, Types, and Treatment

8 minute read time

Mold, which is a form of fungus, is a multicellular organism that comes in many varieties but is generally categorized as indoor or outdoor mold. Unlike fungal infections (like yeast infections, ringworm, or athlete’s foot) which are non-allergic conditions, a mold allergy occurs when the body triggers an immune system reaction to mold exposure, like inhaling airborne mold spores.

A mold allergy can manifest at any age and trigger a range of symptoms, including sneezing, coughing, runny nose, and headaches. Accurately diagnosing an allergy to mold can be difficult. Not only is it puzzling trying to figure out the source or type of mold that’s triggering the immune response, but differentiating a mold allergy from other allergens (like ragweed pollen or dust) can be challenging in and of itself. The symptoms of a mold allergy can also range in severity from person to person. It’s common for some individuals to experience mold allergy symptoms year-round, whereas others may have flare-ups that only occur during certain times of the year.

Some mold spores spread rapidly in dry, windy conditions while other forms are more abundant in humid, moist weather, such as foggy and rainy conditions. If you suspect you have a mold allergy, it’s important to be mindful of where and when you experience symptoms, such as whether you’re indoors or outdoors, and what the environmental conditions are like. This knowledge can equip you and your physician with better awareness as to what’s triggering the allergy and how to treat it.

Testing is an effective way to determine a mold allergy. Once the source has been pinpointed, one can take measures to avoid or remove the mold to prevent future allergic reactions. Medications can also be prescribed to help alleviate mold allergy symptoms, in addition to other potential treatments. Below we discuss in further detail the symptoms, causes, and types of mold allergies, including how to diagnose, treat, and manage the condition.

Mold Allergy Symptoms

The signs and symptoms of a mold allergy can start abruptly upon exposure or have mild symptoms that linger with prolonged exposure. Mold allergy symptoms resemble that of other types of upper respiratory conditions and allergies. They include:

  • Coughing, sneezing
  • Stuffy, runny nose, or postnasal drip
  • Watery, itchy eyes
  • Itchy, sore throat
  • Wheezing, congestion
  • Dry, scaly skin
  • Rash, irritated skin

Exposure to mold, even briefly, can cause a common symptom called mold rash, which is a similar skin condition seen in other forms of allergic reactions. The symptoms of mold rash include raw and sensitive skin, discoloration, itchiness, raised bumps, or dryness. Physical contact or inhalation of mold spores can trigger this rash.

When it comes to indoor mold allergy symptoms, some people can have adverse reactions that grow in severity throughout the day (especially when exposed for long periods of time). In some cases, allergy symptoms to indoor mold can gradually persist long-term, making it difficult to detect.

If you have asthma and a mold allergy, asthmatic symptoms can be triggered when exposed to mold spores. This is particularly problematic with indoor mold and cases of childhood asthma. In most cases, this can cause common symptoms like coughing, wheezing, chest tightness, and shortness of breath. In extreme cases, certain molds can trigger a severe asthma attack.

Causes of Mold Allergy

Over 1,000 species of mold have been identified in homes throughout the U.S. alone. That number doesn’t include the abundance of mold varieties that grow outdoors.

In simple terms, moisture, oxygen, and organic materials are the key factors in facilitating mold growth both indoors and outdoors. Mold can grow on a variety of porous and non-porous materials, especially wood, leaves, foods, fabrics, plastics, and glass, as well as building materials like concrete, metal, insulation, and ceiling tiles. On the surface, mold can look green, gray, black, or other discoloration, which usually depends on the type of mold and its growing environment.

Like mushrooms, yeasts, and mildew, mold is comprised of a network of threadlike filaments that reproduce by releasing spores. These spores are small and lightweight enough to spread through the air, and they can withstand dry conditions and warm/cold temperature extremes.

One of the most common mechanisms behind a mold allergy is inhaling the spores of a particular type of mold, thereby inducing an adverse inflammatory reaction. The reaction is mediated by the body’s immunoglobulin E (IgE) protein, which rapidly triggers the activation of immune cells and the symptoms that come with it.

Beyond allergies, mold exposure is a legitimate health hazard that contributes to a range of irritation symptoms and potentially toxic substances. It’s not uncommon to be exposed to moderate amounts of mold fairly regularly, and most people are largely unaffected by limited exposure. But for some individuals, certain types of mold can trigger an immune response that causes uncomfortable symptoms. Below are common risk factors and types of mold that cause allergy symptoms.

Risk Factors of Developing Mold Allergies

There are certain risk factors that can increase the likelihood of developing a mold allergy. Or if you have a mold allergy, these factors can exacerbate your symptoms. They include:

  • High humidity. Indoor humidity over 50% can increase the probability of mold growing in your home or living space. This is particularly the case in kitchens, bathrooms, basements, and below-ground rooms.
  • Poor ventilation. Closed or no windows, door seals, and weak air circulation can trap moisture and enhance mold-growing conditions. In wintertime, elevated indoor concentrations of molds can increase the risk of allergy symptoms,1 largely due to trapped moisture in buildings for heat retention.
  • Excess moisture. Some homes and workplaces are prone to water seepage during heavy rain and floods, not to mention constant leaky pipes and condensation build-up. Any sources of excessive moisture can encourage mold growth and should be fixed when present.
  • Respiratory conditions. Having a respiratory condition like COPD or asthma can be a risk factor for mold allergy and experiencing intensified symptoms.
  • Family history. If allergies and asthma are common conditions that run in your family, then you may be more susceptible to developing a mold allergy.
  • Occupation. Certain occupations can involve greater exposure to mold compared to others. These occupations include farming and agriculture, carpentry, logging, baking, millwork, dairy work, greenhouse work, and winemaking.

Mold can grow virtually anywhere if the conditions are right. While some situations may be difficult to deal with – like indoor mold allergies in the home or workplace – most scenarios are more predictable and avoidable.

If your home is susceptible to excess humidity or moisture, long cold seasons, or poor ventilation, it’s smart to be mindful of potential mold growth in high-humidity rooms (e.g. kitchen or bathroom), or within walls and framing, carpet and flooring, insulation, and other areas where mold might manifest.

Types of Allergenic Mold

Molds live everywhere and can be difficult to avoid. They’re found on logs and fallen leaves outdoors and in moist places like bathrooms and kitchens indoors. Some individuals are allergic to these molds when exposed, while others are unaffected. Below are some of the most problematic mold species to be conscious of.

Alternaria Alernata

Alternaria alternata is one of the most common types of outdoor mold that can cause hay fever or hypersensitivity reactions that are sometimes associated with asthma. Dustborne Alternaria alternata antigens are also a frequent problem inside the home, according to a U.S. study.2


A widespread indoor and outdoor mold that’s commonly found on living and dead plant material. Cladosporium is an airborne mold that easily grows on carpets, wallpaper, and window sills, as well as on potted plants and soil.


A common form of indoor and outdoor mold that can cause allergic reactions, lung infections, and infections in other organs, according to the CDC. Aspergillus is associated with allergic bronchopulmonary aspergillosis, a severe lung reaction that may cause bronchiectasis (severe widening of the bronchi in the lungs).


A common indoor mold allergy that’s frequently found on decaying vegetation, compost, wood, spices, dry cereals, fresh fruit, vegetables, and soil. Penicillium is most commonly associated with agricultural production, specifically fruit and vegetable spoilage.

Stachybotrys Chartarum

A highly toxic microfungus, Stachybotrys chartarum is one of the most common types of black mold that grows on cotton, wood, paper products, and other organic materials. In addition to triggering allergy symptoms in those who are allergic, Stachybotrys chartarum releases harmful mycotoxins that can cause mold poisoning in anyone with enough exposure.

Typhula Blight

Most commonly called gray snow mold or speckled snow mold, Typhula blight is a type of fungus and a turf disease that damages or kills grass after snow melts, typically in late winter. This pathogen can spread rapidly but is mostly distributed in winter climates that receive adequate snowfall, such as Utah, Wisconsin, Michigan, and Minnesota.3

Mold Allergy Diagnosis

Symptoms of mold allergy often mimic that of other conditions, making it difficult to diagnose. An allergist or immunologist can help you accurately diagnose a mold allergy, typically by way of a skin prick test. Alternatively, you can use a home-to-laboratory allergy testing kit , which is a reliable way to identify mold as an allergy trigger.

Blood tests evaluate your immune system’s response to mold by measuring the amount of immunoglobulin E (IgE) antibodies in your bloodstream. Typically done at home with a simple test kit, a blood sample is sent to an accredited medical laboratory where it can be tested for mold sensitivity.

Exposure to allergenic mold can occur just about anywhere — in the home, outdoors, or at work. Assessing aspects of your home and lifestyle is important to minimize exposure and pinpoint problem areas. If you live, work, or play in a mold-prone environment, you may be able to identify the source of the mold by tracking your symptoms over a period of time, along with where you’ve been.

Treatment for Mold Allergy

Prevention, management, and treatment of mold allergies are the most important measures to take in minimizing unpleasant symptoms. If you’re planning to be around potential sources of mold, such as being outdoors, taking antihistamines, decongestants, and allergy medications in advance can help relieve symptoms. You can also wear a facemask to prevent inhaling mold spores.

While avoiding exposure to allergy triggers is the best way to eliminate symptoms, unfortunately, molds are ever-common and it can be difficult to completely avoid them. Although there’s no guaranteed cure for allergic rhinitis caused by a mold allergy, there are a number of treatments and medications that can relieve symptoms, including:

  • Antihistamines. A popular medication that can help reduce allergy symptoms, like itching, sneezing, and runny nose. With over-the-counter options available, antihistamines work by blocking the inflammatory chemical (histamine) released by the immune system during an allergic reaction.
  • Nasal corticosteroids and sprays. Decongestant nasal sprays help treat and prevent upper respiratory inflammation caused by mold allergies. Often one of the first medications prescribed, corticosteroids and nasals are effective but shouldn’t use long-term.
  • Montelukast. Also known as Singulair, this medication blocks the function of leukotrienes, which are immune system chemicals that contribute to excess mucus and drainage.
  • Oral decongestants. This treatment can help dampen the cold-like allergy symptoms that can result from mold exposure, like congestion, sore throat, and postnasal drip.
  • Immunotherapy. Also commonly known as allergy shots, this is a form of treatment that an allergist can prescribe and is shown effective in providing long-term relief.

To keep allergy symptoms at bay, there are certain lifestyle and home remedies that can help. Dust masks, avoiding the outdoors at certain times, regulating indoor humidity levels, and sleeping with the windows closed are just a few ideas. Managing an allergy requires understanding your unique triggers and how to avoid them.

Indoor Mold Allergy Management & Prevention

In addition to treating symptoms, the other key component in controlling your mold allergies is to guard against mold growth and exposure in and around your home:

  • Avoid using carpet, rugs, and moisture-absorbing materials in bathrooms and basements
  • Be sure all bathrooms are properly ventilated, and use the ventilation fan during showers or baths to minimize moisture accumulation.
  • Use a dehumidifier, especially in areas that are humid, damp, and musty. Keep your humidity levels below 50-60 percent whenever possible.
  • Take measures to prevent sources of dampness in basements, specifically with groundwater runoff and pipe leaks
  • Promote groundwater drainage away from your house and ensure the ground slopes away from the foundation.
  • Remove leaves and vegetation from around the foundation and clean out rain gutters frequently
  • Keep plants and their containers clean and dry, especially those made of organic materials like stone, wicker, or hemp.
  • Use a high-efficiency particulate air (HEPA) filter with air conditioners, furnaces, or other ventilation systems, and change filters regularly.

Consulting a physician, allergist, or immunologist is the best action to take if you suspect a mold allergy. Similarly, using an at-home blood test is a convenient and affordable tool when medical attention isn’t readily available. If symptoms persist before confirming an allergy from a physician or blood lab test, there are numerous over-the-counter medications that can provide relief of common allergy symptoms.


1 Jacob, Beate et al. “Indoor exposure to molds and allergic sensitization.” Environmental health perspectives vol. 110,7 (2002): 647-53. doi:10.1289/ehp.02110647

2 Salo, Päivi M et al. “Dustborne Alternaria alternata antigens in US homes: results from the National Survey of Lead and Allergens in Housing.” The Journal of allergy and clinical immunology vol. 116,3 (2005): 623-9. doi:10.1016/j.jaci.2005.05.030

3 Chang, S W et al. “Distribution of Typhula spp. and Typhula ishikariensis Varieties in Wisconsin, Utah, Michigan, and Minnesota.” Phytopathology vol. 96,9 (2006): 926-33. doi:10.1094/PHYTO-96-0926


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