What Are Allergies?
- An allergic reaction occurs when the immune system responds in an abnormal fashion to a substance that is foreign to the body.
- The immune system normally protects the body from harmful agents like bacteria and toxins.
- The body's abnormal response to a substance that is usually harmless (called an allergen) is called a hypersensitivity reaction, or an allergic reaction. Generally, these reactions are due to interactions between the allergen and the family of proteins, IgE (immunoglobulin E), resulting in activation of cells in the body called mast cells and basophils. These cells release chemical messengers in the body that cause the symptoms of an allergic reaction.
- Many substances in the environment can become allergens but only in genetically susceptible people. Dust mites, molds, animal hair or danders, pollens, medications, foods, and insect venoms are examples of common allergens.
- Reactions may be in the nose (hay fever), eyes (conjunctivitis), chest (asthma), or it can be systemic (anaphylaxis), meaning it can involve the entire body.
- Allergic rhinitis is an inflammation of the nasal membranes (along with membranes of the eyes, eustachian tubes, middle ear, sinuses, and throat) due to an allergic reaction.
- It is the most common cause of inflammation in the nose (rhinitis). Approximately 20% of the U.S. population is believed to suffer from allergic rhinitis.
What Are the Risks of Allergies?
In rare cases, an allergic reaction can be life-threatening, such as with asthma or anaphylaxis (see severe allergic reaction). However, most allergic reactions (for example, hay fever or conjunctivitis) are less serious.
Allergic rhinitis can be associated with other conditions, including asthma, atopic dermatitis, and nasal polyps. It can also have complications such as otitis media, eustachian tube dysfunction, sinusitis, and conjunctivitis. Symptoms of allergic rhinitis can in some cases contribute to or worsen learning difficulties, sleep disorders, and fatigue.
What Medical Treatments Are Used for Allergies and Hay Fever?
Although it is not always possible, one should attempt to avoid contact with known or suspected allergens. (If you have cats and are allergic to cat dander, it is best to reconsider having cats.) At first, some nonprescription antihistamines or decongestants may be tried to decrease nasal congestion (that "stuffed up" feeling), a runny nose, and itching or watery eyes. If symptoms persist, a doctor or health-care professional may prescribe a prescription-strength medication. The following sections discuss some common medications for allergies and hay fever.
Many antihistamine drugs are available without a prescription. Examples include the first-generation antihistamines such as brompheniramine (Dimetapp, Bromphen, Dimetane, Nasahist), chlorpheniramine (Chlor-Trimeton), clemastine (Allerhist, Tavist), and diphenhydramine (Benadryl), and the second-generation antihistamine loratadine (Claritin), cetirizine (Zyrtec), and fexofenadine (Allegra). Loratadine, cetirizine and fexofenadine do not cause drowsiness do not cause or cause less drowsiness than first-generation antihistamines.
Common prescription antihistamines (all second-generation antihistamines) include desloratadine (Clarinex), and levocetirizine (Xyzal). These antihistamines (along with loratadine, cetirizine, and fexofenadine) are less likely to cause adverse effects like drowsiness or dry mouth.
- How antihistamines work: These drugs compete with histamine for histamine receptor sites. Histamine is a chemical released by specialized allergy cells called activated mast cells during the allergic response. By occupying the histamine receptor sites, they prevent histamine from causing the characteristic allergic symptoms. Antihistamines are most effective when taken continuously during the allergy season.
- Who should not use these medications: Antihistamines are contraindicated in individuals allergic to them. They may cause unwanted side effects in the following:
- Use: Antihistamines come in tablet, chewable tablet, capsule, and liquid forms. How often an antihistamine should be taken each day depends on the individual antihistamine's characteristics and the type of preparation (that is, the dosage form).
- Drug or food interactions: Avoid taking other drugs that cause drowsiness, such as alcohol, sleep preparations, sedatives, or tranquilizers. Avoid taking MAOIs (for example, isocarboxazid [Marplan], phenelzine sulfate [Nardil], or tranylcypromine [Parnate]) within 14 days of antihistamines. For drug interactions specific to a particular antihistamine, talk with a doctor or pharmacist.
- Side effects: Many antihistamines (particularly the first-generation agents) may cause the following side effects:
- Dry mouth
- Urine retention
- Blurred vision
- Before driving a car or operating machinery, be sure to know if the antihistamine affects the ability to concentrate and stay awake.
- Check with a health-care provider before taking antihistamines if you are unsure whether or not antihistamines will be appropriate for you.
Pseudoephedrine (Sudafed), naphazoline (4-Way Fast-Acting Nasal Spray), and oxymetazoline (Afrin Nasal Spray) are examples of decongestants. Due to increasing abuse of pseudoephedrine (as a stimulant in athletics and in the illegal production of methamphetamines), phenylephrine has been substituted for pseudoephedrine in many over-the-counter preparations. Phenylephrine is less effective than pseudoephedrine for the treatment of rhinitis symptoms. Many over-the-counter products are available for purchase at the pharmacy counter that contain pseudoephedrine (rather than being freely available on store shelves).
- How decongestants work: These drugs decrease nasal congestion by causing blood vessel constriction (narrowing) and reduced blood flow to the nasal passage.
- Who should not use these medications: These medications should not be used in those who are allergic to them. They may cause unwanted side effects in individuals with the following conditions:
- Use: Decongestants are available over the counter in oral (tablets, capsules, liquids) and nasal-spray forms. Many combination preparations are available that combine decongestants with first- or second-generation antihistamines. The individual preparations vary in regard to how often the drug should be taken each day. Use of nasal sprays as directed should be for temporary relief only (no longer than three to five days). Prolonged use can cause worsening congestion.
- Drug or food interactions:
- Avoid within two weeks of taking MAOIs (for example, isocarboxazid [Marplan], pargyline [Eutonyl], procarbazine [Matulane], and tranylcypromine [Parnate]).
- Use caution with herbal drug preparations that also increase blood pressure, such as ephedra (Ma Huang).
- Illicit drugs (such as cocaine) may also cause increased blood pressure.
- Side effects: Do not use decongestant nasal sprays for more than three to five days. Use beyond three to five days causes swelling in the nasal passages and aggravates allergic symptoms. Oral decongestants may increase blood pressure, cause or aggravate existing heart rhythm abnormalities, and/or cause wakefulness and difficulty falling asleep.
Anticholinergic Nasal Sprays
Ipratropium bromide (Atrovent) is a prescription medication that can be used to reduce runny nose.
- How anticholinergic nasal sprays work: When sprayed into each nostril, anticholinergic nasal sprays decrease secretions from the glands lining the nasal passage. This diminishes the symptom of runny nose.
- Who should not use these medications: Individuals who are allergic to any components of the nasal spray should not take this drug.
- Use: The usual dosage is one to two sprays in each nostril two to three times per day. This is not typically used as a first-line drug in the treatment of hay fever but may be useful in some cases for severe and uncontrollable runny nose.
- Drug or food interactions: Since this spray has little or no effect beyond the area applied, it is unlikely to interact with other drugs.
- Side effects: Anticholinergic nasal sprays may cause an excessively dry nose, thereby causing nosebleeds or irritation.
Corticosteroid Nasal Sprays
Examples of corticosteroid nasal sprays include beclomethasone (Qnasl, Beconase, Vancenase), budesonide (Rhinocort), flunisolide (Nasalide, Nasarel), fluticasone (Flonase), mometasone (Nasonex), ciclesonide (Omnaris, Zetonna), fluticasone furoate (Veramyst), and triamcinolone (Nasacort). Corticosteroid nasal sprays are available by prescription only and are currently the most effective treatment for relief of allergic rhinitis (hay fever).
- How corticosteroid nasal sprays work: These drugs decrease inflammation within the nasal passages, thereby relieving nasal symptoms.
- Who should not use these medications: Individuals who are allergic to any components of these nasal sprays should not use them.
- Use: Gently shake the container. Blow the nose to clear the nostrils. Close (pinch) one nostril, and insert nasal applicator into the other nostril. Inhale through the nose and press on the applicator to release the spray. Apply the prescribed number of sprays and repeat with the other nostril.
- Side effects: These sprays may cause nosebleed or sore throat.
Antihistamine eyedrops, such as azelastine (Optivar), ketotifen (Zaditor), or olopatadine (Patanol), are used to relieve symptoms like itchy or watery eyes. Other eyedrops containing anti-inflammatory agents, such as ketorolac (Acular), or corticosteroid eyedrops, such as loteprednol (Alrex, Lotemax) may also decrease swelling and irritation. Nonprescription eyedrops that are used for allergies and hay fever are also available. These eyedrops contain decongestants (phenylephrine, naphazoline, or tetrahydrozoline) and/or antihistamines (pheniramine or antazoline). Some examples include naphazoline and zinc (Clear Eyes ACR), Naphcon-A, Visine Allergy Relief, and Opcon-A.
- How antiallergy eyedrops work: These drugs decrease inflammation or inhibit histamine release. The result is a decrease in symptoms involving the eye, such as itching, tearing, or swelling.
- Who should not use these medications: The following individuals should not use antiallergy eyedrops:
- Those with allergy to the medication or other components of the eyedrops
- Those with eye infections
- Use: Tilt the head back and use the index finger to pull down the lower eyelid to make a pocket. Use the other hand to hold the eyedrop bottle. Gently squeeze the prescribed number of drops into the eye pocket.
- Drug or food interactions: Using corticosteroid eyedrops at the same time as antiallergy eyedrops may increase the risk of infection.
- Side effects:
- Antiallergy eyedrops may cause temporary stinging or burning when administered, as well as red or watery eyes in some people. If irritation persists, contact the doctor.
- Soft-contact lens wearers should wait at least 10 minutes after using eyedrops to insert contact lens.
- Use care to prevent contamination of dropper tip or eyedrop solution.
- Corticosteroid eyedrops may increase pressure in the eye; therefore, people with cataracts or glaucoma must use them with caution.
Montelukast (Singulair) is a leukotriene inhibitor approved by the U.S. Food and Drug Administration for relief of seasonal allergy conditions and hay fever in adults and in children older than 2 years of age.
- How leukotrienes work: Leukotrienes are chemical substances that promote the inflammatory response seen during exposure to allergens. By keeping these chemicals from producing swelling, leukotriene inhibitors reduce inflammation.
- Who should not use these medications: The following people should not use leukotriene inhibitors:
- Those who are allergic to leukotriene inhibitors
- Those with phenylketonuria (PKU) because the chewable tablets contain aspartame, a component of phenylalanine
- Use: Leukotriene inhibitors are available (with a prescription) in tablet, chewable tablet, and oral granule forms. Granules may be taken directly in the mouth, or they may be mixed in soft foods like pudding or applesauce. These drugs are taken as a once-daily dose.
- Drug or food interactions: No drug or food interactions have been reported.
- Side effects: Leukotriene inhibitors are usually well tolerated and side effects are similar to those of patients taking a placebo (sugar pill). Headache, earache, sore throat, mood effects and respiratory infections have been reported.
Mast Cell Inhibitors
Cromolyn sodium (Nasalcrom, Crolom) is used to prevent allergic symptoms like runny nose or itchy eyes. Cromolyn sodium must be started one to two weeks before pollen season and continued daily to prevent seasonal allergy symptoms. The response is not as strong as that of corticosteroid nasal sprays.
- How mast cell inhibitors work: These drugs prevent the release of histamine and other chemicals that cause allergic symptoms from mast cells when an individual comes into contact with an allergen like pollen.
- Who should not use these medications: Individuals who are allergic to any components of the nasal spray or eyedrops should not take mast-cell inhibitors.
- Use: Frequent dosing is necessary, since the effect only lasts up to eight hours. Mast-cell inhibitors are available as nasal sprays to prevent runny nose or eyedrops for itchy eyes.
- Drug or food interactions: Since these drugs have little or no effect beyond the area applied, they are unlikely to interact with other drugs.
- Side effects: Contact lenses should not be worn if using eyedrops. Eyedrops may cause stinging, burning, redness, and, possibly, severe swelling of eyes. Nasal congestion, sneezing, itching, nosebleeds, and burning have been reported with use of cromolyn sodium nasal sprays.
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Medically reviewed by Michael Manning, MD; American Board of Allergy & Immunology
Sheikh, Javed, and Umer Najib. "Allergic Rhinitis." eMedicine. June 16, 2009. <http://emedicine.medscape.com/article/134825-overview>.
Weiner, J.M., M.J. Abramson, and R.M. Puy. "Intranasal Corticosteroids Versus Oral H1 Receptor Antagonists in Allergic Rhinitis: Systematic Review of Randomised Controlled Trials." BMJ 317.7173 Dec. 12, 1998: 1624-9.