This article originally appeared in the April 2005 Harvard Women’s Health Watch and is provided courtesy of Harvard Health Publications.

What to do when allergic rhinitis is in bloom

Spring brings some of nature’s most irritating allergies into the air, while other allergies occur year-round.

Many of us welcome warm weather as a chance to get outdoors after a winter’s confinement. But for people with hay fever, spring is the beginning of allergy season, and outside can be the worst place to be. Technically known as seasonal allergic rhinitis, hay fever is an immune response provoked by airborne substances, mostly plant pollens and mold spores. The symptoms — sneezing, runny nose, itchy eyes, stuffy sinuses, and tickling throats — aren’t life-threatening, but they can make you miserable. Hay fever can also cause drowsiness, lost work time, and difficulty concentrating.

Allergic rhinitis isn’t just a seasonal problem. Perennial allergic rhinitis, which is triggered by common household substances such as dust mites, animal dander, insect droppings, and indoor mold, can be a year-round annoyance. Neither type of allergic rhinitis can be cured. But better understanding of allergic reactions has led to more effective ways of preventing and treating them.

Why me?
You develop an allergy when your immune system becomes hypersensitive to a normally harmless substance, such as inhaled pollen or dust mite particles or feces. Once sensitized, the immune system overreacts every time it’s exposed, even to very tiny amounts.

Not everyone has allergies. Some people are genetically predisposed (one or both parents have allergies), and others may develop allergies in response to the environment. One theory, called the “hygiene hypothesis,” holds that allergies are the price we pay for protecting our children from germs with modern sanitation and antibiotics. The idea is that lack of exposure to dirt, dust, and certain childhood infections early in life makes the immune system hypersensitive later on. For example, studies in Europe have found that children growing up in regular contact with farm animals and barns have less hay fever than children in rural environments who do not live on farms. On the other hand, repeated exposure to certain allergens, such as dust mites, may further predispose the offspring of allergic parents to develop allergies.

Common offending allergens
A substance that provokes allergic rhinitis in one person may have no effect in another. Some substances are more allergenic than others:

Pollens. These tiny male reproductive cells of flowering plants are ideally suited to travel on wayward breezes — right into your nose, throat, and eyes. Pollen season starts as early as January in southern states; further north, it may begin in March or April and run through October. The major culprits aren’t the big, showy bloomers; their pollen is generally too heavy to become airborne. The real troublemakers are plants whose blossoms are so inconspicuous that you may be hardly aware that they flower.

The most common pollen allergens come from trees (alder, ash, birch, box elder, cypress, elm, hickory, maple, mulberry, oak, poplar, sycamore, walnut, and western red cedar); grasses (Bermuda, blue grasses, orchard, meadow fescue, rye, sour dock, sweet vernal, and timothy); and weeds (burning bush, cockleweed, ragweed, pigweed, Russian thistle, sagebrush, and tumbleweed).

Molds. Though less notorious than pollen, mold spores are an equivalent source of misery. Among the most ubiquitous and allergenic are Alternaria, Cladosporium, Aspergillus, and Penicillium. You can encounter them both indoors and outdoors.

Indoor molds grow in basements, bathrooms, humidifiers, garbage cans — wherever there’s moisture. Outdoor molds, which are active from spring until the first frost, also thrive in damp conditions; they love rotting wood, leaf piles, and compost bins. (Mold spore allergens are not the same as the mold-produced toxins that can make you sick if you eat them.)

Dust mites. These microscopic relatives of spiders and ticks live in fabric — bedding, carpets, and upholstery — and feed off the skin cells we shed. Decayed dust mite carcasses and droppings contain a highly allergenic protein.

Pets and pests. A salivary protein that animals, especially cats, collect on their skin and fur when they groom themselves is a potent allergen. So is the dander, or skin flakes, that pets shed. Rat urine and cockroach droppings also contain allergenic proteins.

Diagnosing allergic rhinitis
If you have seasonal allergic rhinitis, you can often find the agent responsible simply by correlating your symptoms with local pollen and mold counts. You can check the pollen count through local media or on the Web page of the American Academy of Allergy, Asthma, and Immunology’s National Allergy Bureau, www.aaaai.org/nab.

If you have perennial allergic rhinitis, you may need to see an allergist, a physician with training in allergies and the immune system. She or he may suggest some of the following:

Skin tests. The allergist pricks the skin on the inside of your arm or on your back with a needle coated in a suspected allergen, or injects it under the skin. Because the same immunoglobulin E (IgE) antibodies that react to allergens in the respiratory passages are also present in the skin, substances that provoke allergic rhinitis will elicit a skin reaction, in the form of an itchy red swelling, usually within 10–15 minutes.

Histamine is the main substance causing the allergic response to skin tests, so be sure not to take any product containing antihistamine for several days before the test.

Blood test. The allergist draws a blood sample and tests it for IgE antibodies to certain allergens, such as ragweed or cat saliva. A high level of antibody indicates a reaction to that allergen. The test — sometimes called the RAST (radioallergosorbent test) — is usually used in addition to skin testing or as a primary test for people who can’t or don’t want to have skin tests.

Preventing allergic rhinitis
The best way to avoid allergic rhinitis is to identify the allergen and stay away from it. Sometimes that’s easy, but it’s often inconvenient and time-consuming. To get rid of household molds, you may need to dehumidify your home, repair leaks, and discard sources of dampness. To protect yourself from dust mites and pest contaminants, you need to clean house regularly and carefully, seal pillows and mattresses in protective covers, and get rid of wall-to-wall carpeting. To avoid pollen, stay indoors when pollen counts are high, especially on dry, windy days and between 5 a.m. and 10 a.m., when airborne pollen is generally at its worst. (Keep in mind that pollen is counted after it’s settled on the ground, so pollen counts tend to reflect conditions 24 hours earlier, or more.)

Even if a medical treatment reduces your symptoms, you should still try to avoid allergens, to lessen the severity and frequency of attacks.

Anatomy of allergic rhinitis In allergic rhinitis, an allergen — pollen, for example — dissolves in the mucosal lining of the nose, throat, or airways, where it comes into contact with sensitized immune cells called mast cells. These cells carry immunoglobulin E (IgE) antibodies, the result of the body’s earlier encounter with the allergen. IgE-activated mast cells trigger the release of histamines, setting off a process that involves other inflammatory substances, such as leukotrienes and prostaglandins. The resulting dilated blood vessels, inflamed tissues, narrowed nasal passages, and congested sinuses cause sneezing, coughing, wheezing, runny nose, weepy eyes, and itchiness. The reaction may worsen and can damage tissue if it isn’t stopped.

Treating allergic rhinitis
Several medications are available for treating allergic rhinitis, many of them newer, safer versions of older drugs. If you have seasonal rhinitis, starting a medication before the hay fever season begins will reduce your likelihood of developing complications such as sinus infections and blocked ears.

Medical treatments for allergic rhinitis include these:

Antihistamines. These medications, also called H1 antagonists, block the action of histamine, a major cause of allergic rhinitis symptoms. Antihistamines are often recommended first because many of them are available over the counter. Older drugs such as Benadryl or Chlor-Trimeton may make you drowsy. That’s less likely with the newer generation of less-sedating or non-sedating antihistamines (see chart below), such as prescription Allegra and nonprescription Claritin. These drugs can also be taken once a day, instead of every four to six hours. Antihistamines work well for sneezing, runny nose, and itchy, watery eyes, but not as well as nasal corticosteroids for congestion.

Decongestants. If your nose has been stuffed up for a few days, you may need a decongestant. Available in oral and nasal-spray forms, decongestant drugs work on the nervous system to narrow blood vessels, helping to dry up secretions and clear congestion. They can cause dry mouth, nervousness, insomnia, rapid heartbeat, increased blood pressure, and damage to the lining of the nose, so they shouldn’t be used for more than a few days.

Nasal corticosteroids. Anti-inflammatory nasal sprays are the most effective medical treatment for allergic rhinitis. They help turn off the immune reaction in the nasal passages and provide sustained relief. Nasal corticosteroids can irritate the nasal membranes, but they don’t have the troubling side effects associated with oral, injected, or inhaled steroids, such as bone loss and weight gain.

Antileukotrienes. These oral drugs block the effects of leukotrienes, chemicals that cause inflammation. They’re an alternative to antihistamines.
Mast cell stabilizers. These drugs reduce swelling and secretions by interfering with the release of certain chemicals from mast cells (see “Anatomy of allergic rhinitis,” above). They’re very safe but not as effective as nasal corticosteroids.

Immunotherapy. Better known as allergy shots, immunotherapy involves injecting an allergen under the skin in small and increasing doses every week for several months, then monthly for three to five years. The object is to accustom the immune system to the substance so that it doesn’t provoke an allergic attack. Immunotherapy can markedly reduce the need for medication, and it also cuts the risk that allergic rhinitis will progress to asthma. The drug omalizumab (Xolair) represents a different approach to immunotherapy, dubbed anti-IgE. It is FDA-approved only for asthma but has shown promise in preventing allergic rhinitis.