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Allergic conjunctivitis

Conjunctivitis is one of the most common eye diseases and consists of inflammation of the conjunctiva, the thin protective membrane that lines the white part of the eye and the inner surface of the eyelids.

Allergic conjunctivitis occurs when the inflammation is caused by an immune reaction triggered by certain substances (allergens) in the environment, on the skin around the eyes (cosmetics, detergents, medicines) or on other surfaces that come into contact with the eye (hands, eye pencils, etc.).

The most common symptoms of allergic conjunctivitis are generally:

  • itching;
  • swelling of the eyelids;
  • burning and redness of the eyes;
  • abundant tearing;
  • hypersensitivity to light (photophobia);
  • sensation of a foreign body in the eyes (“sand” sensation).

When the allergen is spread in the environment, these may be accompanied by respiratory symptoms typical of rhinitis (repeated sneezing, itching of the nose or palate, nasal secretion and congestion) or bronchial asthma (difficulty breathing, dry cough).

Allergic conjunctivitis is usually distinguished into seasonal conjunctivitis or perennial conjunctivitis depending on the period of spread of the allergen causing it.

The seasonal form is mainly linked to the spread of pollen or spores in the environment during a limited period of the year. In our latitudes, it is more frequent in spring/summer and is usually caused by the flowering of widespread plants (olive, wallflower, hazel, betullaceae, grasses...).

Perennial allergic conjunctivitis, on the other hand, can occur all year round and the main causes are dust mites or animal dander, whose presence in the environment is not tied to a particular season.

Pathology image


The diagnosis of allergic conjunctivitis is made by the ophthalmologist, following an assessment of the symptoms and the appearance of the eye (eyelid swelling, hyperaemia, chemosis, papillary reaction).

The specialist may also examine the eye with a special instrument, the slit lamp, which allows him or her to detect any signs of allergy (such as dilated blood vessels on the eye surface).


Treatment for allergic conjunctivitis usually involves the use of antihistamine and anti-inflammatory eye drops on prescription. The use of artificial tears is also important, both for their power to wash away and dilute the allergens present on the eye mucous membranes, and because they can improve symptoms if refrigerated. Finally, careful cleaning of the eyelids and eyelashes is recommended (preferably without detergents, perhaps with saline solution) to remove allergens that may be deposited there. 

Since the allergic predisposition of each individual generally persists throughout life, in the treatment of allergic conjunctivitis it is important to first remove or avoid as far as possible the responsible allergen. This can be done, for example, by avoiding areas where grass is being cut, or going to the countryside at certain times of the year, or, in the case of mite allergies, by eliminating objects that trap dust in the house and washing bed linen at a temperature above 50°.