Allergic conjunctivitis: an overview of this eye infection

By Cristiano Antonino On Mar 27, 2023

Allergic conjunctivitis is an inflammatory process involving the conjunctiva, the effect of any allergen, both chemical and natural

This type of allergy affects more or less 20% of all allergies, probably becoming the most common type I reaction (immediate hypersensitivity reactions, which develop within an hour of exposure to the antigen).

Although it is so widespread, there is no drug capable of curing it: it is possible to prevent allergic conjunctivitis with specific behavioral hygiene measures.

What can be done, in the event of particularly violent or annoying reactions, is to alleviate the symptoms with specific drugs such as antihistamines or corticosteroids.

What is allergic conjunctivitis?

Allergic conjunctivitis is an acute conjunctival inflammation, it can be both intermittent and chronic.

The cause is usually the presence of specific allergens in the air, for which our body will have a hypersensitivity reaction.

The symptoms are, of course, limited to the eye, although it is not excluded that there may be other reactions caused by certain allergens, such as allergic rhinitis, and are:

Itching
Tearing
Secretions
Conjunctival hyperemia

Like all allergic forms, this type of conjunctivitis is also an abnormal and exaggerated reaction of the immune system in contact with certain antigens.

That is, our antibodies recognize – erroneously – some substances, generally pollen, as potentially dangerous, causing abundant tearing, itching, eyelid edema.

Types and classifications of conjunctivitis

Contrary to what one might think, there is no single type of allergic conjunctivitis, but it is possible to classify different ones both on the basis of the characteristic symptoms and the modalities of appearance, and on the basis of the triggering cause.

As for the first classification, we will have acute and chronic conjunctivitis.

Let’s see them specifically

Acute conjunctivitis. It generally presents rather violent symptoms, such as itching and swelling of the eyelids, but – fortunately – the discomfort subsides in a short time.
Chronic. Less annoying but more persistent than the acute one is chronic conjunctivitis. In addition to antihistamine and vasoconstrictor eye drops, it is necessary to identify the allergen to avoid contact.

A second classification, i.e. by triggering cause, sees four types of allergic conjunctivitis: seasonal, spring, perennial and contact

Seasonal allergic conjunctivitis is caused by mold spores, pollen from trees, or grasses that are in the air only during certain seasons. It follows the life cycle of the responsible plant and therefore it will hardly suffer from it in winter, a period that sees a very low or absent production of pollen. It will then show up in spring (in most cases), late summer or fall.
Spring allergic conjunctivitis particularly affects children and boys between the ages of 5 and 20. It often disappears with adulthood but may also persist. In addition to eye symptoms, you may also develop eczema or asthma. The triggering cause, as the term suggests, is the pollens – numerous and abundant – which are produced in spring by plants.
Perennial allergic conjunctivitis, also known as atopic, is caused not by pollen but by dust, animal hair and other substances unrelated to the changing seasons. For this reason, the symptoms can develop throughout the year whenever the subject is in contact with the substances that trigger the hypersensitivity reaction.
Allergic contact conjunctivitis is mostly caused by reactions to chemicals, such as eye drops or cosmetics. This type of allergy hardly improves with pharmacological treatments, but tends to disappear naturally when contact with the accused substances ends.

Symptoms

Despite these classifications, there are symptoms that all types of allergic conjunctivitis have in common and they are:

Itching in both eyes, which can be more or less intense, sometimes associated with the sensation of having specks in the eye.
Hyperemia (i.e. greater blood flow) to the conjunctiva, the thin mucous membrane that covers the eyeball: the effect is that of having red eyes.
Tearing.
Gelatinous-stringy secretions from the eyes.
Swelling in the eyelids.

In the most serious cases, photosensitivity and eyelid edema may also occur, or even a corneal ulcer may develop (this occurs only between 3 and 11% of patients), which causes severe pain and increased photosensitivity.

Very often allergic conjunctivitis is associated with other typical symptoms of hypersensitivity to substances, such as eczema, allergic rhinitis and asthma.

Causes

As we have seen from the classification, allergic conjunctivitis can have different causes depending on the allergen that triggers the reaction.

So, the element that causes the whole process can be:

natural, and therefore pollen, dust mites or pet hair;
of a chemical nature, such as the substances contained in contact lenses, in some eye drops or in cosmetics.

Diagnosis

A specialist medical evaluation is always important both for the diagnosis, which in any case is quite predictable in the seasonal forms of conjunctivitis or where one realizes that the symptoms are related to exposure to a certain substance, and to evaluate the presence of any pathological alterations of our visual system which over time can produce permanent damage.

So, after the personal assumption of allergic conjunctivitis you will have to go to the ophthalmologist, who will start the visit with an accurate history of necessary information and symptoms.

To better ascertain the causes, he could prescribe a series of specific laboratory tests, let’s see what they are.

Prick test. This is one of the most used tests in the diagnosis of any form of allergy. Through a series of very small painless punctures, the patient’s skin is brought into contact with various substances: skin-type reactions may occur, in this case the test is positive and the allergen responsible for the conjunctivitis will be identified.
Tear fluid test. This test allows you to detect the presence of antibodies, specifically IgE that move to fight – erroneously – the allergen. Therefore, in the presence of IgE, the conjunctival reaction will certainly be allergic.
Conjunctival provocation test. The principle is the same as the prick test: a reaction is sought in contact with the suspect substance, which is placed in very small quantities on the conjunctiva. If you are allergic, of course, you will immediately set off conjunctivitis.

All the tests provided are absolutely non-invasive, it is not necessary to hospitalize or take special measures to perform them.

He will then carry out an objective examination by evaluating the bulbar and tarsal conjunctiva, or below the eyelids, to look for secretions and some morphological changes that can also cause damage to the cornea.

In some forms of allergic conjunctivitis, in particular in vernal keratoconjunctivitis (VKC), there are peculiar modifications of the tarsal conjunctiva which, following inflammation, develops papillae, which in turn cause keratitis with even serious sequelae due to the normal corneal transparency.

Therapy

As we have seen, there is no cure for allergic conjunctivitis.

The best way to avoid the onset of this type of conjunctivitis is to avoid contact with the responsible allergen.

However, when the symptoms are triggered, it is advisable to contact your doctor or an ophthalmologist to start drug therapy.

Antihistamine or corticosteroid eye ointments or eye drops may be prescribed.

For more aggressive allergic reactions, it is possible that the doctor also prescribes oral medications that can counteract the reaction more effectively.

Although it is easily diagnosed and quite widespread, it is good not to overlook allergic conjunctivitis, because as already mentioned it could lead to secondary eye damage if not treated correctly.

Prevention

The best prevention for allergic conjunctivitis is to limit contact with certain substances to a minimum or avoid them altogether if possible.

Unfortunately, as in the case of spring pollen allergy, this is not always possible: in this case we can start a prophylactic therapy a few weeks earlier, both with antihistamines and to strengthen one’s immune system.

Useful tips

Although the decongestant eye drops that are used to combat allergic conjunctivitis are freely available, it is always advisable to contact your doctor before taking them.

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Obviously – advice valid for everyone – do not use medicines that have expired or have been open for more than a week: it could be convenient to buy eye drops in single-dose bottles.

During the acute phase of allergic conjunctivitis do not use contact lenses or cosmetics that could worsen the situation even if they are not the triggering cause of the reaction.

For any action that has to do with the eyes, especially when applying drops or ophthalmic ointment, it is always necessary to wash your hands thoroughly and make delicate movements so as not to scratch your eyes.

Grandma’s Remedies? To reduce swelling and congestion in the eyes, warm water compresses can be used for relief.

The liquid should be slightly above room temperature.

Sometimes compresses with chamomile can be made but in this case you must be sure that it is well filtered because the suspended particles could be irritating; a cotton ball will be soaked and passed over the eye.

The wraps can also be done 2-3 times a day.

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