Allergy Medications – Conditions Treated, Side Effects

allergy medications


Allergy medications are over-the-counter and prescription drugs designed either to prevent or to treat the symptoms of an allergic reaction. Most of these treatments belong to one of four classifications:

  • Antihistamines
  • Decongestants
  • Anti-inflammatories
  • Bronchodilators

Allergy drugs come in many different forms, including pills, nasal sprays and creams. Some are to be taken after symptoms appear, while others are taken regularly to prevent future reactions.

These medications all have potential side effects and may not be suitable for people with certain existing medical conditions. As with any drug, consult a physician before taking allergy medications, whether they are prescription or over-the-counter.

About allergy medications

Allergy medications help treat or prevent the symptoms associated with allergies. They may be recommended to a patient when other forms of treatment have failed. Usually, a physician will suggest lifestyle modifications to avoid the allergen. If this proves unsuccessful or is not practical, allergy medications (sometimes in combination with some lifestyle modifications) may be recommended.

Allergy medications are divided into two categories:

  • Controllers. These drugs work to prevent allergy symptoms from appearing. They interfere with the process that causes inflammation, or prevent the release of the chemicals that trigger symptoms.

  • Relievers. These drugs provide temporary relief once symptoms have appeared. They may be used alone to treat very mild allergies, or with controllers as a long-term treatment plan for moderate to severe allergies.

Some medications, such as antihistamines, work as both controllers and relievers.

The medication a physician recommends will depend in large part on the patient’s symptoms. Other factors physicians will consider include the patient’s overall health and medical history, the severity of the patient’s allergic condition, the patient’s tolerance for certain medications, the physician’s expectations for the course of the condition (i.e., whether this is an acute or more long term process) and the patient’s personal preferences.

Various drugs treat different aspects of an allergic reaction. The most popular medications include:

  • Antihistamines. Medications that work as both controllers and relievers, antihistamines block the work of histamine, a chemical released during allergic reactions. Histamine contributes to symptoms such as hives, sneezing, runny nose and itchy eyes. Antihistamines attach to cell receptors – known as H1, H2 and H3 – and prevent histamine from doing the same. The histamine (which primarily does its work at the H1 receptor) has nowhere to go, short-circuiting the allergic process. Antihistamines typically are taken as pills, nasal sprays, eye drops and skin creams and sprays. 
  • Decongestants. Relievers that treat symptoms of nasal congestion. During an allergic reaction, histamine opens blood vessels in the nasal passage and causes fluid to leak from them. This swells the tissues, narrowing the airway and causing the person to feel stuffy. Decongestants counter this effect by constricting blood vessels, reducing the swelling of nasal tissues and decreasing mucus production. Decongestants usually are available as pills, liquid or syrup, eye drops, nasal drops and nasal spray.

  • Anti-inflammatories. Controller medications that inhibit allergic reactions and reduce nasal swelling. They usually are taken as a nasal spray. Three of the more popularly prescribed anti-inflammatories are:

    • Corticosteroids. Used to treat the most severe forms of allergic rhinitis (hay fever), they decrease inflammation in nasal passages during an allergic reaction. Corticosteroids mimic the behavior of cortisol, a hormone in the body that aids proper body function during stressful situations. This extra boost helps the body fight inflammation. Corticosteroids also can shrink nasal polyps. Corticosteroids generally are taken topically, or inhaled nasally or through the mouth. But they also can be found in pill form and as eye drops. When applied to the skin, these drugs relieve itchiness and prevent rashes from spreading. When placed into the eye as an eye drop, corticosteroids can relieve redness, tearing and itchiness.

    • Cromolyn sodium. The most common mast cell stabilizer, medications that prevent mast cells from bursting and releasing histamine and other chemicals known to cause the symptoms of an allergic reaction. Cromolyn sodium is used to relieve runny nose and sneezing but is not as effective as corticosteroids and cannot be used to treat nasal polyps. However, it has fewer side effects than corticosteroids. It comes in nasal inhaler, oral, eye and nasal spray (nonprescription) form.

    • Leukotriene modifiers. Usually prescribed to treat asthma but may also be prescribed for some people with allergies. Medications within this class have been approved in the United States as a controller drug used to prevent symptoms of allergic rhinitis. Some studies have indicated that these prescription drugs may be more effective when combined with antihistamines, thereby shutting down two major chemicals in airway constriction, histamines and leukotrienes.

      It should be noted that leukotriene modifiers have not been found to be as effective as inhaled corticosteroids, and that there is not yet a body of evidence to conclusively state that leukotriene modifiers are an effective means of treating allergic rhinitis by themselves.

  • Bronchodilators. Medications that open the airway to relieve breathing problems such as shortness of breath, wheezing or chest tightness. They come in several forms, including pills, liquids, injections and inhalers. Some forms are only available by prescription while others are available over-the-counter.

  • Antihistamine/decongestant combinations. Over-the-counter and prescription antihistamine/decongestant combination drugs also are available. This type of medication relieves all mild allergy symptoms a patient might experience.

Epinephrine may be recommended to reverse the symptoms of anaphylactic shock, a rare and severe allergic reaction that is potentially life-threatening. Epinephrine constricts blood vessels, prevents fluid leakage, opens the airways and raises blood pressure.  It also quickly relieves the itching and skin flushing that is part of most anaphylactic reactions. Epinephrine usually is injected in the thigh. Physicians recommend that individuals at risk for anaphylaxis use epinephrine at the first sign of this condition.

Anti-IgE antibodies are newer controller medications used to prevent allergy-related asthma attacks. Research into newer, alternate anti-IgE antibody treatments is ongoing and many of the long-term side effects of this type of therapy are still unknown.

While not medications, allergy shots (immunotherapy) are another form of allergy treatment. Low doses of an allergen are periodically injected into a patient over a period of months or years to increase the patient’s tolerance to the allergen. This reduces symptoms brought on by an allergic reaction. Typically, allergy shots are recommended after use of other medications has failed to tame symptoms, or to prevent cases of whole-body allergic reactions known as anaphylaxis.

Many allergy medications can be purchased over-the-counter at a pharmacy. Others must be prescribed by a physician. Patients should not take any medications without first consulting a physician.

Conditions treated with allergy medications

Most allergy medications are designed to treat symptoms of allergic rhinitis, also known as hay fever. However, these drugs sometimes are also used to treat other allergic conditions, including food allergies and skin disorders related to allergies. Conditions treated with allergy medications include:

  • Rhinitis. Inflammation of the mucous membrane lining the nose that may be caused by an allergic reaction (allergic rhinitis) or other factors, such as an infection (non-allergic rhinitis). Allergy medications are effective at treating the nasal congestion and sneezing associated with this condition.
  • Conjunctivitis. Inflammation of the tissues inside the lining of the eyelid caused by an allergic reaction (allergic conjunctivitis), irritation or infection (pink-eye). Allergy medications (usually administered through eye drops) can help reduce inflammation, relieving symptoms such as red, itchy or watery eyes.
  • Sinusitis. Inflammation of the lining of the sinus cavities in the face that can be caused by allergies (allergic sinusitis), infection or irritation. Allergy medications can reduce the inflammation, relieving symptoms such as sinus pressure, runny nose and congestion.
  • Bronchitis. Inflammation of the bronchial tube linings caused by allergies (allergic bronchitis), irritation or infection. Short-acting allergy medications can relieve the persistent cough and shortness of breath associated with this condition.

  • Anaphylactic shock. A potentially life-threatening condition that involves difficulty breathing and a drop in blood pressure as the result of exposure to an allergen. It can be treated with allergy medications.

  • Asthma. A condition in which airway passages become blocked or constricted causing shortness of breath. Some allergy medications open the airways by relaxing the smooth muscles or decreasing the amount of mucus that can potentially narrow airways.
  • Atopic dermatitis. An itchy inflammation of the skin, often characterized by flaking, caused by an allergic reaction. Histamine levels appear elevated in the skin and plasma of some individuals with this condition, making allergy medications a useful treatment.

  • Hives. Red, swollen patches of skin that often itch or burn that can be treated with allergy medications.

  • Wheezing. A whistling sound caused by the friction of air going through narrowed airways. Allergy medications widen the narrow passageways and relax the small tubes in the lungs, making breathing easier.

  • Lung disorders. Allergy medications may be used to treat a number of conditions that may impact a patient’s ability to breathe.

  • Ear-related problems. Allergy medications may be used to treat a number of ear-related disorders that may be linked with allergies.

Conditions of concern with allergy medications

Patients with a history of certain health problems should use caution when taking allergy medications. They also should disclose certain lifestyle information to physicians before taking the medication. These conditions include:

  • Previous allergic reactions to medications
  • Other allergies, including those to pollens and foods
  • Urinary tract problems
  • Prostate problems
  • Heart disease
  • Glaucoma (a group of diseases that affect the optic nerve, which connects that eye to the brain)
  • Stomach ulcers
  • Thyroid disease
  • Liver disease
  • High blood pressure
  • Intestinal obstruction
  • Kidney disease
  • Diabetes mellitus
  • Blood vessel disease
  • Asthma
  • Emphysema
  • Chronic bronchitis
  • Amebiasis (a parasitic infection)
  • Injuries to the nose, or sores inside the nose
  • Osteoporosis (a bone disease)
  • Pregnancy or breastfeeding
  • Pheochromocytoma (a rare tumor)
  • Arrhythmias (heart rhythm disorders)

Potential side effects of allergy medications

All allergy medications have the potential to create side effects in patients, although the severity of these may differ. Side effects most commonly associated with allergy medications include:

  • Drowsiness
  • Fatigue
  • Impaired coordination
  • Dry nose, mouth and throat
  • Diarrhea, constipation or abdominal discomfort
  • Blurred vision
  • Difficulty urinating or urine discoloration
  • Headache
  • Nervousness, anxiety, restlessness or insomnia
  • Irritability
  • Decreased appetite
  • Fluid retention or weight gain
  • Increased blood pressure
  • Rapid pulse
  • Increased sneezing
  • Nose or throat irritation (e.g., burning, stinging, soreness, hoarseness)
  • Nosebleeds
  • Coughing
  • Bad taste in the mouth
  • Wheezing
  • Skin rash
  • Nausea
  • Muscle cramps or tremors
  • Dizziness or lightheadedness
  • Backache
  • Tingling of the hands and feet
  • Nightmares (usually in children)

Potentially more serious, less common side effects include:

  • Weakened immune system
  • High blood sugar levels
  • Temporary psychosis (a mental condition that causes people to lose touch with reality)
  • Hallucinations
  • Severe nausea or vomiting
  • Heart palpitations (an awareness of a strong, fast, irregular, abnormal or “galloping” heartbeat)
  • Chest pain
  • Severe headache
  • Fever or chills
  • Swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs
  • Worsening of symptoms

Prolonged use of corticosteroids can lead to Cushing’s syndrome, a hormonal disorder resulting from extended exposure of the body’s tissues to high levels of cortisol. Symptoms include:

  • Round or full face
  • Weight gain
  • Weakness
  • Thirst
  • Increased fat around the neck
  • Increased urination
  • Depression

Long-term corticosteroid use may also lead to ulcers, cataracts (a clouding of the eye’s lens), osteoporosis (a disease in which the bones are weakened, increasing the risk of fractures) and easy bruising.

Prolonged use (more than three or four consecutive days) of over-the-counter nasal spray or eyedrop decongestants can cause a “rebound” of symptoms called rhinitis medicamentosa. This involves swelling of the nasal membrane and an increase in nasal obstruction. To avoid the rebound effect, patients are advised to use the smallest dose possible as infrequently as possible. This effect is not a concern with prescription medications.

Drug or other interactions

Patients should consult their physicians before taking any additional prescriptions, over-the-counter medications, nutritional supplements or herbal medications. Of particular concern for those taking allergy medications are:

  • Other allergy medications. Unless under a physician’s direction, can increase the risk of side effects or overdose.
  • Cold and flu drugs. May contain alcohol or allergy medications, which can increase the risk of side effects or overdose.
  • Prescription pain medications. The effects of these medications may be increased when used in conjunction with antihistamines.
  • Muscle relaxants. The effects of these medications may be increased when used in conjunction with antihistamines.
  • Large amounts of aspirin or anticoagulants (medications that inhibit the blood’s ability to clot). Can increase the risk of stomach bleeding or ulcers when used with corticosteroids.
  • Seizure medications. The effects of these medications may be increased when used in conjunction with antihistamines or bronchodilators. Seizure medications can also decrease the effectiveness of corticosteroids and may decrease blood levels of some bronchodilators.
  • Anesthetics. The effects of these medications may be increased when used in conjunction with antihistamines.
  • Sedatives. The effects of these medications may be increased when used in conjunction with antihistamines. Sedative use can also decrease the effectiveness of corticosteroids.
  • Antihypertensives (medications used to treat high blood pressure). The effectiveness of these drugs may be reduced when used in conjunction with bronchodilators.
  • Antiarrhythmics (medications used to treat abnormal heart beats). The effectiveness of these drugs may be reduced when used in conjunction with bronchodilators.
  • Ulcer medications. Can interfere with the function of bronchodilators or lead to a build up in the blood.
  • Immunosuppressants (drugs that suppress the immune system). Can interfere with the function of corticosteroids.
  • Psychiatric medications. Use of some bronchodilators in conjunction with certain medications used to treat psychiatric disorders may lead to potentially dangerous drop in blood pressure and/or rapid heartbeat.
  • Monoamine oxidase inhibitors (an antidepressant). Can increase the risk of serious side effects if used within two weeks of decongestants.
  • Diabetic medications (e.g., insulin). Can interfere with the function of corticosteroids, requiring changes in dosage.
  • Tuberculosis medications. Can decrease the effectiveness of corticosteroids.
  • Antibiotics. Can increase the blood levels and toxicity of corticosteroids or bronchodilators.
  • Antifungals. Can lead to a build up of corticosteroids in the blood, increasing toxicity.
  • Alcohol. Can increase the sedative effects of some allergy medications.
  • Caffeine. Can increase the side effects of bronchodilators in large amounts.
  • Smoke. Smoking or exposure to second-hand smoke can interfere with the way the body responds to certain bronchodilators.
  • Cocaine. Can interfere with heart function and increase the risk of side effects from decongestants.
  • Beta blockers or angiotensin-converting enzyme (ACE) inhibitors. While epinephrine (which constricts blood vessels) is highly effective in treating anaphylaxis symptoms, its effect can be diminished by beta blockers or angiotensin-converting enzyme (ACE) inhibitors (which prevent blood-vessel constriction). These drugs are prescribed to treat high blood pressure and some heart conditions.

Symptoms of allergy medication overdose

Symptoms of overdose can be similar to the medication’s side effects, but are usually more severe. Patients exhibiting any of these signs and symptoms of overdose should contact their physician immediately:

  • Marked sedation

  • Reduced mental alertness

  • Palpitations (an awareness of a strong, fast, irregular, abnormal or “galloping” heartbeat)

  • Apnea
  • Cardiovascular collapse (a sudden loss of adequate blood flow to body tissues)

  • Hallucinations

  • Tremors

  • Seizures

  • Dry mouth

  • Flushed skin

  • Fixed, dilated pupils

  • Extreme tiredness

  • Sweating

  • Dizziness

  • Slow heartbeat

  • Difficulty breathing

  • Fluid retention

Pregnancy use issues with allergy medications

Pregnant women should always consult their physician before using any type of allergy medication. While some allergy medications are considered safe, others may pose a risk to the fetus. If a pregnancy is being planned, it is best to ask about medications prior to becoming pregnant.

Breastfeeding mothers also should contact their physicians before taking allergy medications. While many allergy drugs are not passed through breastmilk in significant amounts, the effects of others are unknown. In addition, some allergy medications can lower the amount of milk produced by the mother.

Child use issues with allergy medications

Children can safely use some allergy medications, as long as they are given in an age-appropriate dosage. However some side effects – such as drowsiness or hyperactivity – can be more exaggerated in children.
Never give medication to a child before consulting a physician. Drugs and their potential effects on children include:

  • Antihistamines. Many antihistamines cause drowsiness in adults, and this effect can become even more pronounced in children. Conversely, other children become extremely jittery after taking antihistamines. Other symptoms that may appear in some children (especially under age 6) include insomnia, nervousness, euphoria, tremors and seizures.

  • Decongestants. These drugs are related to adrenaline, and can make some people jittery. Children are particularly susceptible to this effect, and should take only decongestants formulated for their age group.

  • Corticosteroids. Some injected and oral corticosteroids may impact growth in children and affect the adrenal gland (kidney portion that secretes natural steroids). Children (aged 6 to 12) usually are prescribed corticosteroids in nasal form or inhaler form only, with dosage amounts adjusted for their age and size. Corticosteroids may be less effective in treating infants under the age of 1 year.
    Cromolyn sodium. Because of its relative absence of side effects, cromolyn sodium can be safely used by children as young as 2.

  • Bronchodilators. These are generally used on an as-needed basis when a child is coughing, wheezing or short of breath. Studies performed to date have not demonstrated specific problems that would limit the usefulness of bronchodilators in children.

Elderly use issues with allergy medications

Elderly patients may be more susceptible to the side effects of some allergy medications. In addition, older users should refrain from using a controlled-release or long-acting form of some allergy medications.

Questions for your doctor

Preparing questions in advance can help patients have more meaningful discussions with their physicians. Patients may wish to ask their doctor the following questions related to allergy medications:

  1. Which allergy medication do you recommend for me?

  2. How effective are the medications you have recommended for me?

  3. How will I know if my allergy medication is working?

  4. How and when should I take my allergy medication?

  5. Will I have to take allergy medication for the rest of my life?

  6. How will allergy medication affect my current medical conditions other than allergies?

  7. How will allergy medications interact with other medications I am currently taking?

  8. What side effects may I develop from taking allergy medication?

  9. What side effects should I immediately report to you?

  10. What will be the next step if my current form of medication fails?
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