Reference range:

Alternaria alternata is one of the most common fungi associated with asthma. Not only the presence of asthma but also persistence and severity of asthma have been strongly associated with sensitization and exposure to A alternata. Although exposure to Alternaria is an important risk factor for asthma, few studies have assessed exposure to this fungus in indoor environments.

A alternata, a cosmopolitan saprophyte commonly found in soil and plants, is usually considered an outdoor allergen.

Although most intense exposure is likely to occur outdoors, Alternariaand other allergenic fungi are also found in indoor environments.

Note: All allergens are reported down to a cutoff level of 0.10 kU/L. The significance of allergen specific IgE levels between 0.10 and 0.35 kU/L remains undefined. Cumulative levels of multiple allergen specific IgE antibodies may have an additive effect in producing clinical symptoms. Individual allergen specific IgE antibody levels may not always correlate with severity of clinical symptoms. Results must be interpreted in the context of the clinical history and the patient’s symptom presentation. Quantitative IgE levels can serve to guide overall disease management by targeted trigger exposure reduction to identified allergens.

The most prevalent mold in dry, warm climates, Alternaria alternata has air spores that peak in the afternoon and typically disseminate in warm, dry air. Therefore, in temperate climates, Alternaria alternata spore counts are usually highest in the summer.

Those allergic to this mold may experience symptoms after inhaling its spores. Alternaria alternata is mainly an outdoor fungus that typically grows on vegetation. However, the species can also be found indoors, where it prefers humid locations such as bathrooms and often produces large brown spores that are a well-known cause of allergy and asthma.

That said, indoor Alternaria alternata concentrations are typically impacted by the current amount of outdoor concentrations. That is, if there are considerable spores in the outdoor air, indoor levels may be high as well.

Alternaria thrives at temps of 20 to 25 C (68 to 77 F), but it can survive temperatures between 1 and 35 C (roughly 34 and 95 F).

Mold sensitization rates vary according to different studies, but allergy to Alternaria alternata seems to affect roughly 5 percent of people and is strongly associated with allergic rhinitis (aka hay fever) and asthma. In children, the prevalence of reported sensitization varies dramatically, from less than 1 percent in Austria to 50 percent in the U.S. state of Arizona. And according to a large study of children with asthma living in inner cities in the United States, Alternaria was the most common mold allergy, with 38 percent of study participants incurring a positive skin test to this allergen.

Alternaria allergy paired with Alternaria exposure is a risk factor for the development and worsening of allergic diseases such as allergic rhinitis and asthma, and it can cause severe asthma exacerbations.

Where is Alternaria found?

Alternaria is often found in soil and on mediums such as plants, cereal grains, grass, corn silage, rotten wood, bricks, canvas, iron, compost, and bird nests. Plus, Alternaria is a plant pathogen and can infect more than 4,000 plant species, causing significant damage to grains, fruits, and vegetables, making it responsible for 20 percent of agricultural yield losses. In fact, Alternaria molds grow on a host of foods such as tomatoes, cucumbers, cauliflowers, peppers, apples, melons, tangerines, oranges, lemons, and sunflower seeds.

That said, mold reproduces via spores, which can be transported by air, water, and insects. So even if a fungus originates outdoors, it often can enter a dwelling through a variety of means, including doorways, windows, vents, and heating and air conditioning systems.

Therefore, Alternaria alternata can be found indoors on surfaces such as drywall, ceiling tiles, wood, carpet, wallpaper, textiles, window frames, and materials within heating and air conditioning systems.

Common Symptoms

Mold allergy symptoms can range from mild to severe and vary person to person. Reactions can happen almost immediately after exposure, or they can be delayed. Symptoms are most common in mid-summer to early fall, but since molds grow both indoors and out, allergic reactions can occur all year.

Symptoms typically include one or more of the following:

→ Nasal congestion

→ Runny nose

→ Sneezing

→ Irritated, watery eyes

→ Coughing

→ Wheezing

→ Itchy eyes, nose, and throat

→ Dry, scaly skin

Mold sensitization is also a major risk factor for developing upper and lower respiratory diseases such as asthma. In fact, exposure to Alternaria mold is related to potentially life-threatening asthma. Other reactions to Alternaria can include allergic rhinitis (aka hay fever), allergic sinusitis, and fungal ball production in the sinuses.

A small percentage of asthmatics with inhaled mold allergy can also develop allergic urticaria (aka hives) when they eat or drink anything containing yeast or mold.11 In addition to causing allergic reactions, molds can also lead to infections along with toxic reactions.

How do I manage my allergy?

If you are allergic to molds, your healthcare provider may recommend a plan that includes the following:

Exposure Reduction:

→ Limit your outdoor time during seasons when mold is most active.

→ Wear a mask when disturbing or moving plant materials, and avoid raking and burning dry leaves.

→ Avoid barns, silos, hay, straw, and peat moss.

→ Use a certified asthma and allergy friendly filter attachment on your heating and air conditioning unit, and change filters regularly.

→ Employ dehumidifiers to lower indoor humidity levels to less than 45 percent to create an environment where mold is less likely to thrive.

→ Improve air flow through rooms by opening doors between spaces, moving furniture away from the walls, and operating fans.

→ Use exhaust fans in bathrooms and kitchens to pull moisture out of the rooms.

→ Fix any plumbing leaks, check windows for condensation, and remove sources of dampness.

→ Repair roof leaks, clean gutters, and ensure rainwater drains away from your dwelling.

→ Clean thoroughly and regularly, including sinks and tubs, refrigerator door gaskets, and garbage cans.

→ Remove clothes from washing machines promptly and clean rubber seals regularly.

→ Eliminate sources of dampness in basements, such as pipe leaks and groundwater seepage.

→ Run ventilation fans during and after showers and baths.

→ Remove any carpet from bathrooms and basements.

Symptom Relief:

Your healthcare provider may direct you to employ one of the following therapies to improve your allergy symptoms:

→ Antihistamines are commonly used to reduce symptoms such as sneezing, itching, and runny nose.

→ Nasal corticosteroids are used to reduce swelling in the nose and block allergic reactions.

→ Oral and nasal spray decongestants can be employed to relieve stuffiness.

→ Anti-inflammatories such as montelukast can be effective in treating mold allergy.

→ Daily nasal lavage using a squeeze bottle filled with salt water can help clean out irritants and alleviate nasal symptoms.

→ Allergen immunotherapy, as directed by your healthcare provider, may help develop tolerance to mold exposure.


Exposure to Alternaria alternata in US homes is associated with asthma symptoms (link)

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Fukutomi, Yuma & Taniguchi, Masami. (2015). Sensitization to fungal allergens: Resolved and unresolved issue. Allergology International. 145. 10.1016/j.alit.2015.05.007. Available from:

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Pomes A, Chapman MD, Wünschmann S. Indoor Allergens and Allergic Respiratory Disease. Curr Allergy Asthma Rep. 2016 Jun;16(6):43. doi: 10.1007/s11882-016-0622-9. PMID: 27184001; PMCID: PMC4976688.

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Lee HB, Patriarca A, Magan N. Alternaria in Food: Ecophysiology, Mycotoxin Production and Toxicology. Mycobiology. 2015 Jun;43(2):93-106. doi: 10.5941/MYCO.2015.43.2.93. Epub 2015 Jun 30. Erratum in: Mycobiology. 2015 Sep;43(3):371. PMID: 26190916; PMCID: PMC4505009. Available from:

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