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.