How Do Intranasal Antihistamines Work?

Intranasal antihistamines are drugs used to treat allergic rhinitis (irritation and swelling of the mucous membrane in the nose occurring seasonally or year-round) or vasomotor rhinitis (blood vessels in the nasal mucosa dilate and cause congestion). Histamine is a chemical produced by cells in response to allergens. These drugs block the release of histamine and relieve symptoms caused by histamine such as sneezing, runny nose, and postnasal drip. 

Intranasal antihistamines inhibit the release of histamine from mast cells (specialized immune cells) and other mediators that are involved in allergic responses.  

Corticosteroids having anti-inflammatory characteristics have effects on various cells, including mast cells and eosinophils, and inflammatory mediators (e.g., histamine, eicosanoids, leukotrienes, and cytokines). The administration of intranasal antihistamines along with such corticosteroids is believed to be beneficial and improve nasal symptoms.

Olopatadine intranasal/mometasone combination drug is yet to be approved by the U.S Food and Drug Administration for the treatment of allergic rhinitis.

Intranasal antihistamines are available as nasal sprays for the treatment of:

• Seasonal allergic rhinitis
• Perennial allergic rhinitis
• Vasomotor rhinitis

Side effects associated with intranasal antihistamines include:

• Bitter taste
• Vomiting
• Headache
• Dizziness
• Drowsiness
• Somnolence (feeling of lack of energy)
• Application site irritation
• Upper respiratory tract infections
• Cough
• Dyspnea (breathlessness)
• Dry mouth
• Nasal burning
• Sneezing
• Weight gain
• Contact dermatitis
• Eczema
• Itching
• Involuntary muscle contractions
• Edema 
• Hypertension (high blood pressure)
• Tachycardia (rapid heartbeats)
• Vertigo
• Menstrual disturbances
• Urinary retention
• Confusion 
• Blurred vision
• Conjunctivitis (inflammation of the conjunctiva)
• Xerophthalmia (dry eyes)
• Anaphylaxis (life-threatening allergic reactions)

The information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of intranasal antihistamines include:

• Astelin Nasal Spray
• Astepro
• Azelastine
• Azelastine HCl
• Olopatadine intranasal
• Olopatadine intranasal/mometasone, intranasal (Pending FDA approval)
• Patanase
• Rhinolast
• Ryaltris