Indoor Allergens

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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What about allergies to indoor pollens and houseplants?

It is surprising, considering how frequently outdoor pollens cause allergies, that few indoor plants are troublesome. Indoor plants are more leafy than flowering and do not pollinate as much as outdoor plants. Some offending indoor plants are the weeping fig (Ficus benjamina), which can cause eye allergies, and the flowering maple (Alutilon hybridum), which can cause asthma.

Indoor plants, especially those that are kept in damp wicker baskets, are a source of molds. Plant terrariums and large indoor plants are culprits as well. Dried flowers and live Christmas trees should also be avoided, as they are common carriers of molds.

Table 1: Where Animal Allergens Come From
CatSkin, Saliva
DogSkin, Saliva
Guinea PigUrine, Saliva
RabbitUrine, Saliva
GerbilSkin, Serum

What is the treatment for allergic reactions to indoor allergens?

Avoidance of identified indoor allergens can be very effective in controlling allergy symptoms. If such avoidance is not possible or incomplete, antihistamines are a common treatment for reactions to indoor allergens. These are medications that fight the effects of the histamine released during an allergic reaction by blocking the action of the histamine on the tissue.

The so-called first-generation antihistamines include diphenhydramine (Benadryl), chlorpheniramine (Chlortrimaton), dimenhydrinate (Dramamine), brompheniramine (Dimetapp and others), clemastine fumarate (Tavist, Allerhist), and dexbrompheniramine (Drixoral). Dryness of the mouth and sleepiness are well-known side effects of first-generation antihistamines. Newer second-generation antihistamines, sometimes referred to as non-sedating antihistamines, include loratadine (Claritin), fexofenadine (Allegra), cetirizine (Zyrtec), fexofenadine (Allegra), and azelastine (Astelin Nasal Spray). These second-generation antihistamines typically have a slower onset of action, are longer acting, and do not have the sedating effects of the first-generation antihistamines.

Decongestants are drugs that reduce swelling in the nasal passages. These drugs can be helpful in reducing allergy symptoms, but they do not treat allergic reactions. Decongestants are available as pills or tablets or can be taken by nasal spray. Decongestant nasal sprays often cause a so-called "rebound effect" or worsening of symptoms if taken for too long, so they should not be used for more than five days without a doctor's recommendation. They should be used with caution in people with heart disease.

Prescription medications, including corticosteroids, cromolyn, and ipratropium (Atropine-like) nasal sprays, are used to manage some allergy symptoms. Montelukast (Singulair) is an inhibitor of a chemical involved in allergic reactions known as leukotriene. Montelukast is used to treat asthma and has also been approved for treatment of hay fever (allergic rhinitis).

Allergy immunotherapy (allergy shots) is a process of stimulation of the immune system with gradually increasing doses of the substances to which a person is allergic. Immunotherapy is very effective for management of allergies to pollen, mites, cats, and especially stinging insects (for example, bees). This treatment usually requires a series of injections and takes up to one year to become effective. The required length of treatment varies, but a typical course of treatment lasts about three years.

Can reactions to indoor allergens be prevented?

Symptoms and signs of allergic reactions to indoor allergens can only be prevented to the extent that the allergens can be avoided or removed from the environment. Sometimes immunotherapy, as described above, can help prevent or decrease the severity of allergic reactions.

Indoor allergens testing

Diagnostic testing is possible to establish whether someone is allergic to common indoor allergens. Both skin tests and antibody tests may be used. Skin testing using the scratch or skin prick method involves placing a small amount of the test substance onto the skin, then pricking or scratching the skin so that the allergen enters the skin. An allergic reaction typically takes place within 15 to 20 minutes. Another type of skin test that generally shows an immediate reaction is the intradermal skin test, in which a small amount of the substance to be tested is injected beneath the skin surface, as with a TB (tuberculin) skin test.

With patch skin testing, test substances are taped to the skin for 48 hours, and the area is then observed for signs of an allergic reaction.

Skin testing for allergies is the most common way to determine if someone is allergic, but in some cases, allergy blood tests are used. These tests look for specific antibodies. Both the enzyme-linked immunosorbent assay (ELISA, or EIA) and the radioallergosorbent test (RAST) are tests to identify allergen-specific antibodies in a blood sample. Since the introduction of the ELISA test, RAST testing is less common.

Indoor allergens and mold test kit

A number of manufacturers offer indoor allergen and mold test kits that can be used to obtain samples of air or other substances in the home that are sent for analysis to a professional laboratory. A number of providers also offer air quality and allergen testing services.


"Indoor Allergens." American Academy of Allergy, Asthma, and Immunology.

Medically Reviewed by a Doctor on 10/22/2015

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