RELATED STORIES • Humidifiers: Vital steps for cleaning • Aspergillosis

Note: All links within content go to MayoClinic.com

Mold allergy is less common than you'd think, given the thousands of types of mold in the environment. Out of all those types, though, only a few dozen cause an allergic reaction.

Because molds, or fungi, grow in all kinds of weather and thrive indoors and outside, mold allergy doesn't always have a defined season like pollen allergy does — although several outdoor molds are most highly concentrated from spring to late fall.

If you have asthma caused by mold allergy, the best defense is to avoid sources of mold spores — airborne seeds you can easily inhale. Completely avoiding a substance as common as mold may be difficult, though. Fortunately, asthma and allergy medications can relieve the symptoms of mold allergy.

People with mold allergy experience the same signs and symptoms that occur in other types of respiratory allergies:

• Sneezing
• Runny or stuffy nose
• Cough and postnasal drip
• Itchy eyes, nose and throat
• Watery eyes
• Skin rash
• Sinusitis, an inflammation of the sinuses

Some people with mold allergy may experience allergy-related asthma, which can be serious in the event of an asthma attack. Signs and symptoms of asthma include:

• Coughing
• Wheezing
• Shortness of breath

When you come in contact with mold spores, your body recognizes them as foreign invaders and develops antibodies to fight them. After the exposure has passed, you still produce antibodies that "remember" this invader, so that any later contact with the mold causes your immune system to react. This reaction triggers the release of substances called histamines, which cause itchy, watery eyes, runny nose, sneezing and other allergy symptoms.

A few years ago, headlines were full of scary reports about a substance called toxic black mold, which allegedly caused serious lung disease and rendered countless homes unfit to occupy. "Black mold" is a nonmedical term that usually refers to the greenish-black mold that results from heavy water damage — a type of mold that has not been conclusively linked to severe mold reactions. Scientists are still trying to understand the health effects of exposure to molds, but many experts believe that reactions to them have not been widespread or common enough to be a significant health problem.

Risk factors for mold allergy include:

• Genetic predisposition to allergies. If one or both of your parents had allergies, you're more likely to develop them too.
• Working in an occupation that consistently exposes you to mold. Occupations where mold exposure may be high include farming, dairy work, logging, baking, millwork, carpentry, greenhouse work, winemaking and furniture repair.
• Living in a house with a wet basement or high humidity. If your indoor humidity is higher than 50 percent or if you have leaky pipes or water seepage during rainstorms, mold may be growing in your home. Mold can grow virtually anywhere if the conditions are right — behind walls in framing, on soap-coated grout and other damp surfaces, in carpet pad and in the carpet itself. Exposure to high levels of household mold may trigger mold allergy symptoms.
• Living in a newer house. New houses have airtight windows and doors, which promote energy efficiency — sometimes a little too well. Tight window and door seals may trap moisture indoors and prevent proper ventilation, creating ideal conditions for mold growth. Damp areas, such as bathrooms, kitchens and basements, are most vulnerable.

If you experience stuffy nose, sneezing, watery eyes and other symptoms for longer than two weeks, see your doctor. You may have allergies.

Mold allergy may be responsible if your symptoms flare up when you're in a musty basement, outdoors raking leaves or mowing the lawn, or anywhere after a heavy rain. Your doctor will consider your symptoms and possibly order tests to determine if you have allergies — and what you're allergic to.

First, the doctor will ask you about your specific symptoms and collect information about family members with allergies. Next, you may need a skin or blood test to determine what you're allergic to.

The most accurate test for mold allergy is an allergy skin test. The test uses weakened extracts from common or suspected allergens, such as molds found in the local area. During the test, these extracts are injected one by one just under your skin or applied to tiny scratches or punctures in your arm or back. If you're allergic to any of the extracts, you'll develop a red, sometimes swollen area in the spot where it was injected or applied.

If you have eczema or another widespread skin disease, you may have a severe reaction to a skin test. Instead, you can safely have a blood allergy test, which, like a skin test, detects allergic sensitivity to specific substances. An allergy blood test is also the alternative to skin testing if you're taking a medication that may cause inaccurate skin test results.

Serious allergic reactions to mold are rare. However, exposure to high levels of mold can cause complications in people whose immune systems aren't operating at optimum levels. If you're healthy, you can handle mold exposure, but if you're on chemotherapy or immune-suppressing drugs, try to avoid damp, musty areas. The same caution is warranted if you have AIDS, an infection, cystic fibrosis or diabetes.

In addition, researchers have found that people with mold allergy are at increased risk of having a life-threatening asthma attack. If you have mold allergy and asthma, be sure you have an emergency plan in place in case of a severe asthma attack.

Medical treatment for mold allergy is similar to treatment for other allergies, with the goal of relieving symptoms.

Medications
Several types of medications are available for asthma and allergic rhinitis caused by mold allergy, depending on the type and frequency of symptoms.

For asthma:

• Inhaled corticosteroids. If you have asthma symptoms more than twice a week, your doctor may prescribe a daily inhaled corticosteroid to control the asthma. Examples include fluticasone (Flovent HFA), beclomethasone (Qvar), budesonide (Pulmicort Turbuhaler) and mometasone (Asmanex). Other medications combine inhaled corticosteroids with long-acting inhaled bronchodilators, such as fluticasone/salmeterol (Advair).
• Bronchodilators. These are quick-acting relief medications that stop the symptoms of an asthma attack in progress. The most commonly used short-acting beta-2 agonist for asthma is albuterol (Proventil HFA, Ventolin HFA).

For allergic rhinitis:

• Antihistamines. When the immune system "overreacts" to an allergen, it releases substances called histamines, which cause itchy, watery eyes, runny nose, sneezing and other symptoms. Antihistamines block this release, providing symptom relief. Common antihistamines are loratadine (Claritin), cetirizine (Zyrtec), and fexofenadine (Allegra).
• Decongestants. These medications help clear mucus from the nose and sinuses, providing relief from congestion, swelling and discomfort. Decongestants are sometimes used in combination with antihistamines to control allergy symptoms. Common antihistamine-decongestant combination drugs include desloratadine and pseudoephedrine (Claritin-D), cetirizine and pseudoephedrine (Zyrtec-D), and fexofenadine and pseudoephedrine (Allegra-D).
• Nasal sprays. Corticosteroid nasal sprays reduce mucus production and swelling in the nose and are effective in reversing allergic reactions to mold. Products in this category include fluticasone (Flonase), mometasone (Nasonex), budesonide (Rhinocort Aqua) and flunisolide (Nasarel).
• Cromolyn sodium. In some people, cromolyn sodium in nasal spray form (Nasalcrom) prevents nasal symptoms from starting.

Immunotherapy
This treatment — a series of allergy shots — virtually eliminates some allergies, such as hay fever. Unfortunately, however, allergy shots are only moderately effective against mold allergy. Current research seeks to improve immunotherapy for mold allergy.

The most important thing you can do to prevent mold allergy is to reduce mold growth in your home. Consider these tips:

• Eliminate sources of dampness in basements, such as pipe leaks or groundwater seepage.
• Use a dehumidifier in any area of your home that smells musty or damp. Remember to clean the collection bucket and condensation coils regularly.
• Use an air conditioner, and consider installing central air conditioning with a high-efficiency particulate air (HEPA) filter attachment. The HEPA filter can trap mold spores from outdoor air before they're circulated inside your home.
• Keep humidity levels well below 50 percent.
• Change furnace and air conditioning filters regularly.
• Be sure all bathrooms are properly ventilated, and run the ventilation fan for 30 minutes following a shower or bath to dry the air.
• Clean bathroom and basement wall surfaces regularly with a bleach solution.
• Promote ground water drainage away from your house by removing leaves and vegetation from around the foundation and cleaning out rain gutters frequently.
• Keep organic plant containers, such as those made of straw, wicker or hemp, clean and dry.

To keep mold allergy symptoms at bay, take these measures:

• Sleep with your windows closed. The concentration of airborne mold spores is greatest at night, when the weather is cool and damp.
• If you must rake leaves, mow your lawn or work around compost, consider wearing a dust mask over your nose and mouth to keep mold spores out.
• Don't go outdoors immediately after a rainstorm, or in foggy or damp weather.

Allergies of any kind can be disruptive and uncomfortable. If you discover that your house is the source of your symptoms, cleaning out and fixing sources of mold can be overwhelming — and expensive. Once the problem is resolved, however, maintaining a mold-free environment should be fairly simple. Then, if you are careful to avoid outdoor mold spores, your house can be your protection from troublesome allergy symptoms.