Get a better understanding of eye Allergic Conjunctivitis with our guide. Learn about the causes, symptoms, and treatment options available to help you find relief.

Allergic Conjunctivitis

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Syed Intisar Hussain

Overview

Allergic conjunctivitis is an eye inflammation triggered by an allergic reaction to allergens, such as pollen or mold. 
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Conjunctivitis, also called pink eye, is an infection of the conjunctiva, a translucent membrane that lines the eyelids and the eyeball. When the conjunctiva is inflamed and swollen, little blood vessels become more noticeable. This is what gives the whites of the eyes a reddish or pink appearance.

Allergic conjunctivitis results from an allergen-induced inflammatory reaction. Allergens such as pollen, dust, mold, and pet dander can all induce an allergic reaction.

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Over the past few decades, allergic illnesses have drastically increased<a href="#accordion">[1]</a>. An estimated 40% of the population is affected by allergic conjunctivitis<a href="#accordion">[4]</a>. It is particularly more common during hay fever season and in areas with high pollen counts and seasonal allergies.

Though conjunctivitis can be bothersome, it rarely impairs vision. Moreover, it is not contagious and cannot spread from person to person. 
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Allergic conjunctivitis is typically divided into seasonal and perennial. 
 
Seasonal Allergic Conjunctivitis

Seasonal allergies correlate with seasonal allergic conjunctivitis, typically occurring in the spring and summer and occasionally in the fall. It mostly occurs due to pollen, grass, and other airborne allergens exposure. Pollen is the most common cause. Symptoms typically last a few weeks and occur at the same time each year. Most people will have other symptoms of hay fever, including sneezing, runny nose, fever, and sore throat. 
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<h5>Perennial Allergic Conjunctivitis</h5>

The perennial form is present all year and is usually due to indoor allergens, such as animal dander, dust mites, and mold spores. It has a milder presentation.

The following are the more severe and less common forms of allergic conjunctivitis. 
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<h5>&nbsp;Vernal Keratoconjunctivitis (VKC)</h5>

This type of conjunctivitis seems to occur due to a combination of allergen and climate. Its exact etiology remains unclear. It is more common in tropical climates than in northern climates. In Europe, the prevalence of VKC ranges from 1.2 to 10.6 cases per 10,000 people<a href="#accordion">[1]</a>. Young people (less than 10 years old) with a history of <a href="https://merisehat.pk/disease/asthma">asthma </a>or atopy are most commonly affected. Moreover, VKC is more commonly seen in men.

Ocular itching, redness, swelling, and discharge are some common symptoms of VKC. Itching can be severe and even incapacitating. Patients frequently experience severe photophobia. The most distinguishing feature is giant papillae on the upper tarsal conjunctiva. These &#39;cobblestone-like&#39; swellings can be several millimeters in diameter. Typically, 10-20 are seen when the upper eyelid is &lsquo;flipped&rsquo;. 
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<h5>Atopic Keratoconjunctivitis</h5>

Atopic keratoconjunctivitis (AKC) is a chronic inflammatory disease of the eyelid and ocular surface that affects both eyes. Its pathomechanism includes chronic mast cell degranulation mediated by IgE and immune mechanisms mediated by Th1 and Th2 lymphocyte-derived cytokines. Most cases occur in 30 to 50-year-olds, with a male predominance. More than 90% of cases occur with atopic dermatitis<a href="#accordion">[4]</a>. 
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<h5>Contact Conjunctivitis</h5>

Also known as contact keratoconjunctivitis, the condition most commonly results from eye drops, cosmetics, and other chemicals that may act as irritants.

Although contact allergic reactions are most commonly seen on the skin, including the skin of the eyelids, the conjunctiva may also be involved in contact allergic reactions. It may take several days for a contact allergen to cause sensitization. When the allergen is re-exposed, an indurated, erythematous reaction develops gradually. The response may peak 2-5 days following re-exposure. Itching is a common occurrence in contact allergic reactions. 
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<h5>Giant Papillary Conjunctivitis</h5>

This is an uncommon type of allergic conjunctivitis. The conjunctiva lining the upper eyelid becomes inflamed, most commonly in contact lens wearers. While the exact cause is unclear, it is believed that an accumulation of debris behind the lens or poor lens hygiene leads to an allergic reaction. Approximately 5% of contact lens wearers are affected by giant papillary conjunctivitis<a href="#accordion">[4]</a>. Moreover, people who wear hard contact lenses after eye surgery are also prone to developing the condition. 
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<h5>Acute Allergic Conjunctivitis</h5>

This is a temporary condition that occurs more frequently during allergy season. There is a sudden development of symptoms such as itching, burning, and swelling of the eyelids. People may also suffer from a stuffy nose.

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<h5>Chronic Allergic Conjunctivitis</h5>

Chronic or persistent allergic conjunctivitis can occur at any time of year. It is an allergic reaction to allergens such as dust and animal dander. Common symptoms include burning and itching of the eyes and light sensitivity. 
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Signs and Symptoms

In most cases of allergic conjunctivitis, both eyes are involved. Symptoms typically appear soon after contact with the allergen.

<ul>
	<li>Red, itchy, watery eyes</li>
	<li>A burning sensation in the eyes</li>
	<li>Sneezing</li>
	<li>Blocked, or runny nose</li>
	<li>Light sensitivity</li>
	<li>Eyelid swelling</li>
	<li>Red, cracked, or dry eyelids (contact conjunctivitis) 
	&nbsp;</li>
</ul>

Note: If your eyes become painful, red, sensitive to light, and your vision feels blurry, contact a healthcare professional immediately. 
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Causes

Exposure to allergens results in the body instigating an immune response to defend itself. It does this in response to stimuli that cause histamine release. The body produces histamine to combat foreign invaders

These are some of the substances that cause this reaction:

<ul>
	<li>Household dust</li>
	<li>Tree and grass pollen</li>
	<li>Mold spores</li>
	<li>Animal dander</li>
	<li>Fragrances are derived from chemicals, such as household detergents or perfume. 
	&nbsp;</li>
</ul>

Certain medications or substances dropped into the eyes like medicated eye drops or contact lens solution can also cause allergic conjunctivitis in some people. 
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There are currently no screening tests for allergic conjunctivitis. The patient&rsquo;s clinical presentation typically points doctors toward the diagnosis. 
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Diagnosis

To diagnose allergic conjunctivitis, the healthcare provider will examine the individual&rsquo;s eyes and go over the allergy history. In addition, they may order one of the following tests: 
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<ul>
	<li>An allergy skin test exposes the skin to allergens and allows the healthcare provider to observe the body&#39;s reaction, including swelling and redness.</li>
	<li>A blood test can determine whether the body produces antibodies against allergens like mold or dust.</li>
	<li>Conjunctival scrapings may be used to assess for white blood cells, such as eosinophils which are typically raised in allergic conjunctivitis. However, the absence of eosinophils on conjunctival scraping does not rule out an allergic conjunctivitis diagnosis. 
	&nbsp;</li>
</ul>

Treatment

There are numerous treatment options for allergic conjunctivitis. 
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<h5>Home Care</h5>

The following home remedies can help treat allergic conjunctivitis.

<ul>
	<li>Rubbing of the eyes should be avoided as it can aggravate symptoms.</li>
	<li>Eyes should be rinsed with saline eye drops or artificial tears.</li>
	<li>A cool compress can be applied to reduce discomfort and inflammation.</li>
	<li>Sunglasses and a hat should be worn to shield the eyes from pollen.</li>
	<li>A shower should be taken after coming in from outside, especially if pollen is a trigger.</li>
	<li>Hands should be washed before touching the eyes, especially after handling pets or other allergens.</li>
	<li>Contact lenses should not be used till the symptoms have resolved. 
	&nbsp;</li>
</ul>

<h5>Medications</h5>

In more complex cases, home care may not be sufficient. A healthcare professional will then advise the following options.

<ul>
	<li>Ocular antihistamines - Antihistamine eye drops are available over-the-counter to reduce or block histamine release. They help reduce itching, swelling, and redness.</li>
	<li>Ocular decongestants - These eye drops help constrict the small blood vessels in the eye, reducing redness. However, they are not recommended for long-term use as using them for more than a few days can worsen symptoms.</li>
	<li>Ocular lubricants - If an individual has dry eyes and does not make enough tears, this can worsen their symptoms. Therefore, in such cases, lubricant drops can ease symptoms.</li>
	<li>Ocular steroids - If other medicines are ineffective, doctors may prescribe steroid eye drops. However, these can raise intra-ocular pressure and cause vision damage. Moreover, the doctor also needs to check for viral eye infections before administering the steroids.</li>
	<li>Ocular mast cell stabilizers - Medications such as Cromolyn work by preventing mast cells from releasing histamine. They typically work best when used before the start of symptoms.</li>
	<li>Oral medications&nbsp; - Oral versions of the above medications are only used in severe cases.</li>
	<li>Allergy shots - These are effective in treating allergic conjunctivitis caused by allergies. 
	&nbsp;</li>
</ul>

Allergic conjunctivitis rarely poses a serious health risk. However, in rare and severe cases, it can lead to the following complications.

<ul>
	<li>Scarring in the eye can result from a severe case of allergic conjunctivitis.</li>
	<li>Keratitis, an inflammation of the cornea, can occur with giant papillary conjunctivitis and dermatoconjunctivitis. It presents with ulcers on the cornea.</li>
	<li>In some cases, allergic conjunctivitis can develop into infective conjunctivitis. 
	&nbsp;</li>
</ul>

Among the risk factors for allergic conjunctivitis are: 
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<ol>
	<li>Allergy history in the family: Allergic conjunctivitis is more likely if one or both of the individual&rsquo;s parents have a history of allergies.</li>
	<li>Personal allergy history: People with existing allergic conditions, such as asthma, eczema, or hay fever,&nbsp; are more likely to develop allergic conjunctivitis.</li>
	<li>Environmental factors: Vulnerability to allergens such as pollen, dust mites, animal dander, and mold can increase the risk of developing allergic conjunctivitis.</li>
	<li>Contact lens use: Because contact lenses trap allergens and irritants against the eye, they may increase the risk of developing allergic conjunctivitis.</li>
	<li>Age: Allergic conjunctivitis can affect people of all ages, but children and young adults are more likely to develop it.</li>
	<li>Gender: Allergic conjunctivitis is more common in women than in men.</li>
	<li>Seasonal factors: Allergic conjunctivitis can be seasonal, with symptoms worsening at particular times of the year, like in the spring or fall when there are high pollen counts. 
	&nbsp;</li>
</ol>

It&#39;s crucial to remember that not everyone with these risk factors will experience allergic conjunctivitis; additionally, some people who don&#39;t have any risk factors might still experience the condition. 
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Avoiding environmental triggers is the best way to prevent allergic conjunctivitis, but this can be challenging. According to the trigger, it might be beneficial if:

<ul>
	<li>Only fragrance-free soaps and detergents are used</li>
	<li>An air purifier is installed in the house</li>
	<li>The house is routinely vacuumed and dusted</li>
	<li>The home&#39;s carpets, soft furnishings, soft toys, and curtains are kept to a minimum. 
	&nbsp;</li>
</ul>

Key Points

<ul>
	<li>Allergic conjunctivitis is an inflammation of the conjunctiva, the transparent tissue covering the white part of the eye.</li>
	<li>Pollen, dust mites, animal dander, mold, and other allergens are the cause, triggering an allergic reaction.</li>
	<li>One may experience redness, itching, swelling, tearing, and a burning sensation in the eyes as symptoms.</li>
	<li>Avoiding allergens, using artificial tears to relieve dryness, taking antihistamines orally, topical anti-histamines and mast cell stabilizers, and using corticosteroid eye drops in severe cases are all part of the treatment.</li>
	<li>Immunotherapy may be recommended in some cases to provide long-term symptom relief. 
	&nbsp;</li>
</ul>

[1] La Rosa M, Lionetti E, Reibaldi M, Russo A, Longo A, Leonardi S, et al. Allergic conjunctivitis: a comprehensive review of the literature. Ital J Pediatr. 2013;39:1–8.

[2] Bielory L, Friedlaender MH. Allergic conjunctivitis. Immunol Allergy Clin North Am. 2008;28(1):43–58.

[3] Ono SJ, Abelson MB. Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol. 2005;115(1):118–22.

[4] Baab S, Le PH, Kinzer EE. Allergic Conjunctivitis. [Updated 2022 May 23]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.