Overview

Allergic conjunctivitis is a type of conjunctivitis specifically caused by allergens (foreign substances that induce allergic reactions). It is a common eye condition that causes both eyes to become irritated. This is often referred to as “pink” or “red” eye. Substances such as pollen or dust are common causes of this condition.

They can cause the eyes to become red, itchy, swollen, and watery due to inflammation of the conjunctiva (a protective membrane lining the eyelids and white of the eyes). In this article, we will explore the causes and types of allergic conjunctivitis and how to diagnose and treat it. 

Causes and types of allergic conjunctivitis

Causes of allergic conjunctivitis

Allergic conjunctivitis is caused by allergens, such as:¹

• Pollen
• Dust mites
• Mould spores
• Pet dander (shed skin particles)
• Chemicals
• Fragrances

Types of allergic conjunctivitis

There are different types of allergic conjunctivitis. These are based on the type of allergen. 

Simple allergic conjunctivitis

This is the most common type of allergic conjunctivitis and is caused by allergens, such as dust, pollen, and pet dander.¹

Seasonal allergic conjunctivitis

This type of allergic conjunctivitis is more commonly known as ‘hay fever’. As the name suggests, this form is mainly associated with seasonal allergies. It is caused specifically by pollen during the spring/summer, which causes an allergic reaction.¹

Perennial allergic conjunctivitis

“Perennial” means this type of conjunctivitis can occur throughout all seasons of the year. It is usually caused by allergens, such as dust mites, pet dander, and mould spores.

Vernal keratoconjunctivitis (VKC)

VKC is caused by exposure to allergens and the climate. The exact cause is not well understood. There are three forms:²

• Palpebral VKC: This type affects the upper part of the eye and can involve the cornea (clear part of the eye)
• Limbal VKC: This type is more common in people of African and Asian descent, affecting the area around the cornea
• Mixed VKC: Combines features of both palpebral VKC and limbal VKC

Atopic keratoconjunctivitis

This is caused by several factors, such as exposure to allergens, the skin condition atopic dermatitis, and genetics.³

Giant papillary conjunctivitis (GPC)

GPC is caused by objects, such as:⁴

• Contact lenses
• Prosthetics
• Stitches

In this form of conjunctivitis, your eyelids become inflamed, red, and swell. Bumps called papillae may also form on your eyelid.

Symptoms of allergic conjunctivitis

Common signs of allergic conjunctivitis include:¹

• Red eyes
• Itchy eyes 
• Watery eyes
• Watery discharge
• Swelling of the eyelids
• Sensitivity to light
• For VKC cases, individuals often complain about a foreign body sensation in the eye

Diagnosis

To diagnose allergic conjunctivitis, a member of the ophthalmology clinical team can use a slit-lamp (a special microscope with a bright light) to examine the front part of the eye (i.e., the eyelids, cornea, iris, and lens). Further tests may also be conducted, such as blood tests and skin prick tests, to ascertain which allergens an individual may react to.

Treatment options

Individuals with allergic conjunctivitis are advised to adhere to the following list to reduce ocular discomfort:¹ 

• Avoid eye rubbing 
• Use artificial tears
• Use cool compresses
• Receive education about good eye practices

For mild cases of allergic conjunctivitis, individuals can use over-the-counter antihistamine drops.⁵ For VKC or atopic keratoconjunctivitis cases, combinations of antihistamine and mast cell stabilising drops or corticosteroid drops can be used under medical supervision.^1,6 

FAQs

How to tell the difference between pink eye and allergic conjunctivitis?

Generally, people refer to all types of conjunctivitis as “pink eye”, regardless of whether the condition was caused by infection or allergens. Bacterial conjunctivitis usually causes the eyes to produce thick yellow/green discharge, that is contagious. Whereas allergic conjunctivitis makes the eyes produce more watery discharge, in this case, it is not contagious. People with viral conjunctivitis also produce watery discharge that looks similar to allergic conjunctivitis, however, the condition is contagious.

Does allergic conjunctivitis need antibiotics?

Allergic conjunctivitis is not caused by an infection. Antibiotics are only prescribed to treat bacterial eye infections. Instead, antihistamines are recommended. 

When should I see a doctor about allergic conjunctivitis? 

Most cases of allergic conjunctivitis do not require a further check-up. However, consult your healthcare provider if you have:

• Changes in your vision (i.e., wavy lines, flashing, more blurred over time)
• Pain continues to persist 
• Light sensitivity (photophobia)
• Intense redness in one or both eyes
• A baby less than 30 days old with red, sticky eyes

These symptoms (above) may be indicative of a more severe problem, so seek further advice in these cases. 

Summary 

Allergic conjunctivitis is a common eye condition where both eyes become irritated due to allergens like pollen, dust, and pet dander. Individuals with allergic conjunctivitis can experience symptoms, such as red, itchy, and watery eyes.

There are different types of allergic conjunctivitis, including seasonal (caused by pollen), perennial (caused by dust or pet dander), and more severe forms related to skin conditions, or objects such as contact lenses. Diagnosis involves an eye exam, and treatment options range from encouraging individuals to avoid allergens and using artificial tears. Advanced treatments include antihistamines or steroid eye drops for more severe cases.