What is Allerex Eye Drop?

October 7, 2025 •

4 min read

Allergic conjunctivitis is estimated to affect approximately 10% to 30% of the general population worldwide. For many, relief comes from products like Allerex Eye Drop. So, what is Allerex Eye Drop and how does it work?

Quick Summary

Allerex Eye Drop is a combination medication containing an antihistamine (Pheniramine) and a decongestant (Naphazoline). It provides temporary relief from itchy, red eyes caused by common allergens like pollen, dust, and animal dander.

Key Points

Dual Action: Allerex Eye Drops contain an antihistamine (Pheniramine) to stop itching and a decongestant (Naphazoline) to reduce redness.
Primary Use: It is used for temporary relief of symptoms associated with allergic conjunctivitis, like itching and redness from pollen or dander.
Mechanism: Pheniramine blocks histamine, while Naphazoline constricts blood vessels in the conjunctiva to clear redness.
Important Warning: Do not use for longer than recommended by a healthcare professional or product label, as overuse can cause rebound redness.
Contact Lenses: You must remove contact lenses before using these drops and wait at least 10-15 minutes before reinserting them.
Administration: Apply by pulling down the lower eyelid to form a pocket and dropping the liquid in without the tip touching the eye.
Check Before Use: Do not use the drops if the solution has changed color or appears cloudy.

Understanding Allerex Eye Drops and Allergic Conjunctivitis

Allergic conjunctivitis, the condition Allerex Eye Drops are designed to treat, affects a significant portion of the population, with estimates suggesting a prevalence of 10% to 30%. This condition occurs when the conjunctiva, the thin membrane covering the white part of your eye and the inside of your eyelids, becomes inflamed due to an allergic reaction. Common triggers include pollen, grass, animal dander, and dust mites. The body's response involves releasing histamine, which leads to the classic symptoms of itching, redness, watering, and swelling.

Allerex Eye Drop is a common over-the-counter (OTC) solution for these symptoms. It is a combination medication, meaning it contains more than one active ingredient to provide comprehensive relief. While the brand name "Allerex" may vary, the core components are typically Pheniramine Maleate and Naphazoline Hydrochloride. These ingredients are found in many well-known allergy eye drop brands, such as Opcon-A, Naphcon-A, and certain Visine products.

How Allerex Eye Drops Work: The Dual-Action Mechanism

The effectiveness of Allerex Eye Drops comes from its two active ingredients working together.

Pheniramine Maleate (The Antihistamine): This component works by blocking histamine, the chemical your body releases during an allergic reaction. By preventing histamine from acting on the cells in your eyes, Pheniramine directly targets and reduces the itching and swelling associated with allergies.
Naphazoline Hydrochloride (The Decongestant): This ingredient is a vasoconstrictor. It acts on the alpha-adrenergic receptors in the small blood vessels (arterioles) of the conjunctiva. This action causes the blood vessels to narrow, or constrict. The result is a visible reduction in eye redness and a decrease in puffiness and irritation. The effects of Naphazoline are rapid, with vasoconstriction occurring within 10 minutes of application and lasting for several hours.

Proper Usage and Application

Correct application is crucial for both safety and effectiveness. Always follow the specific directions on the product label or from your healthcare provider.

Here is a step-by-step guide for proper administration:

Wash Your Hands: Before touching your eyes or the dropper bottle, wash your hands thoroughly to prevent infection.
Remove Contact Lenses: If you wear contact lenses, you must remove them before using these eye drops. Wait at least 10 to 15 minutes after application before reinserting them. Do not use the drops at all if your eyes are red.
Prepare the Drop: Tilt your head back, look up, and gently pull down your lower eyelid to create a small pocket.
Administer the Drop: Hold the dropper directly over your eye and squeeze one drop into the pocket. Be careful not to let the tip of the bottle touch your eye, eyelid, or any other surface to avoid contamination.
Close and Wait: Gently close your eye for one to two minutes to allow the medicine to be absorbed. You can press lightly on the inner corner of your eye (near the nose) to prevent the drop from draining into your tear duct.

Potential Side Effects and Important Warnings

While generally safe for short-term use, Allerex Eye Drops can cause side effects. Most are mild and temporary.

Common Side Effects:

Stinging or burning in the eye upon application
Temporarily blurred vision
Dilated pupils
Mild eye irritation or itching

Serious Side Effects (Stop use and contact a doctor):

New or worsening eye pain or redness
Vision changes
An allergic reaction to the drops themselves, indicated by a rash, hives, or swelling

Important Precautions:

Duration of Use: Do not use these drops for longer than the recommended duration specified on the product label or by a healthcare professional. Prolonged use of the decongestant (Naphazoline) can lead to a condition called rebound hyperemia, where the eye redness worsens.
Medical Conditions: Consult a healthcare professional before use if you have heart disease, high blood pressure, diabetes, or narrow-angle glaucoma.
Contamination: Do not use the product if the solution changes color or becomes cloudy.

Comparing Allergy Eye Drops


Drop Type	Primary Active Ingredient(s)	Primary Use	How It Works	Common Brands
Antihistamine/Decongestant	Pheniramine, Naphazoline	Quick relief of itching and redness	Blocks histamine and constricts blood vessels	Opcon-A, Naphcon-A, Visine-A
Mast Cell Stabilizer	Ketotifen, Olopatadine	Long-term prevention and relief	Prevents mast cells from releasing histamine	Zaditor, Alaway, Pataday
Lubricating (Artificial Tears)	Varies (e.g., glycerin)	Relief from dryness and irritation	Supplements natural tears, hydrates eyes	Refresh, Systane

Conclusion

Allerex Eye Drop, and similar formulations containing Pheniramine and Naphazoline, serve as an effective and accessible option for fast, temporary relief from the uncomfortable symptoms of allergic conjunctivitis. Its dual-action formula tackles both the root cause of itching and the resulting redness. However, it is essential to use these drops correctly, be aware of potential side effects, and understand that they are intended for short-term use only. For chronic or severe symptoms, consulting an eye doctor is crucial to explore long-term management strategies, such as mast cell stabilizer eye drops or other prescription treatments.

For more information on eye health, you can visit the BrightFocus Foundation.

Frequently Asked Questions

Allerex Eye Drops typically contain two active ingredients: Pheniramine maleate, which is an antihistamine, and Naphazoline hydrochloride, which is a decongestant.

The decongestant component, Naphazoline, begins to work quickly, with effects such as reduced redness often seen within 10 minutes of application.

No. You should always remove your contact lenses before applying Allerex Eye Drops. Wait at least 10 to 15 minutes after using the drops before putting your contacts back in.

Overuse, especially for extended periods, can lead to a condition called rebound hyperemia, where the eye redness can return and become worse once the drops wear off.

It is both. Allerex is a combination product that contains an antihistamine (Pheniramine) to relieve itching and a decongestant (Naphazoline) to reduce redness.

The most common side effects are temporary stinging or burning upon application, blurred vision, and potential dilation of the pupils. These effects are usually mild.

Yes, you should tell your care team if your symptoms do not start to get better within the timeframe recommended on the product label or by your healthcare provider, or if they get worse. You may need a different type of treatment.