Conjuntivitis Alérgica, Causas, Síntomas y Tratamientos
Allergic conditions arise from an exaggerated response by the immune system to external stimuli (allergens) in susceptible individuals.
A variety of genetic, environmental, animal and dietary factors, along with early exposure to these during childhood, have led to a significant increase in allergic problems over recent decades.
Ocular allergy is one of the most common conditions encountered in daily clinical practice, and this term encompasses a broad group of conditions involving different immunological mechanisms but sharing common signs and symptoms, which we will explain below.
What do we mean by allergic conjunctivitis or ocular allergy?
Allergic conjunctivitis refers to a group of acute, recurrent and sometimes persistent inflammatory conditions of the ocular surface that can affect the eyelids, conjunctiva and cornea to varying degrees.
These are hypersensitivity reactions triggered by various allergens to which the affected individual reacts, following prior sensitisation or exposure to the allergen.
The reaction is usually bilateral, meaning it affects both eyes simultaneously.
It may occur as an isolated condition or be associated with another allergic disorder.
Causes of Allergic Conjunctivitis and its classification
In previously sensitised patients, inflammation occurs as a result of direct contact between an allergen and the conjunctival surface, via an immediate or immunoglobulin (IgE)-mediated mechanism, triggering the release of various cellular mediators of inflammation by mast cells. Other mechanisms may also be involved in this inflammatory process: neurogenic, endocrine and immune reactions that contribute to the onset of the signs and symptoms characteristic of this condition.
Depending on the nature of the causative allergen, ocular allergy may occur only during certain months of the year or throughout the year. They are therefore classified as:
Seasonal:
This is the most common form of ocular allergy and is linked to seasonal allergens such as ragweed pollen, grass pollen and tree pollen, particularly during spring. It frequently affects young adults (aged 20–40), with no gender predominance, and is often associated with allergic rhinitis and bronchial asthma.
Perennial:
These are associated with year-round allergens such as house dust mites (>50% of cases), pet fur and dander (cats, dogs, birds, etc.), mould and occupational allergens. Symptoms occur throughout the year, although they may worsen at certain times of the year. There is no predominance in terms of age or gender, and the prevalence of association with allergic rhinitis and other forms of allergy is higher than with the seasonal form.>
Spring or Vernal:
In this form, the hypersensitivity response is non-specific, which explains the presence of ocular symptoms induced by stimuli from various environmental factors such as wind, dust and sun exposure. It occurs in children and adolescents aged 11–13 years, with a predominance in males.
Allergic conjunctivitis affects 1 in 4 people
Clinical manifestations
The main symptom of an allergic reaction is itching. It is usually accompanied by:
Stinging (the most characteristic sign)
Red, swollen or itchy eyes
Burning
Watery eyes
Watery, slightly mucous discharge
Swollen eyelids due to fluid build-up, especially in the morning
Sensitivity to light (photophobia)
Foreign body sensation
All these symptoms can appear in different patterns and follow different courses depending on the type of ocular allergy affecting the patient.
Symptoms of Seasonal Allergic Conjunctivitis
In Seasonal Allergic Conjunctivitis, the condition affects both eyes, with a sudden or acute onset of severe eye itching, watery eyes and a burning sensation, along with a runny nose and nasal itching, as well as frequent sneezing. There may be blurred vision, hyperaemia and chemosis of the conjunctiva, as well as a watery-mucous discharge. The cornea is rarely affected.
Symptoms of Perennial Allergic Conjunctivitis
In Perennial Allergic Conjunctivitis, itching and watery eyes are the predominant symptoms, although it is also common for patients to report a foreign body sensation, a sensation of retrobulbar throbbing, and other non-specific symptoms.
Symptoms of Vernal Keratoconjunctivitis
In Vernal Keratoconjunctivitis, the inflammatory process is chronic, with flare-ups in the spring, but also in the autumn and, in some cases, in summer and winter. Itching can be very intense and worsens in the afternoons and evenings; eye redness, watery eyes and photophobia worsen with exposure to sunlight and on windy, dusty days.
Papillae form on the upper eyelid conjunctiva, taking various shapes and accompanied by copious mucous discharge.
The skin of the lower eyelid usually shows characteristic infraorbital darkening (dark circles).
Unlike the seasonal and perennial forms, in vernal keratoconjunctivitis the cornea is usually quite affected and may progress to ulceration with the formation of white-greyish vernal plaques.
Diagnosis
Diagnosis should begin by identifying the clinical signs and be followed by laboratory tests to help confirm the diagnosis.
The medical history should include a family history of ocular allergy and the presence of other forms of allergy, primarily allergic rhinitis, atopic dermatitis, bronchial asthma and urticaria.
Key demographic data such as age at symptom onset, gender, geographical location and environmental conditions are very important for determining the type of allergic ocular disease. The time of year when symptoms begin or worsen, the presentation, progression and clinical manifestations, particularly itching, red eyes and watery eyes, are key factors in the diagnosis.
In the case of giant papillary conjunctivitis, it is important to remember that the most significant factors for diagnosis are a history of contact lens use, eyelid surgery or the use of an ocular prosthesis, as well as the improvement or resolution of symptoms and signs upon removal or discontinuation of such use.
For contact dermatoconjunctivitis, the diagnosis is essentially clinical and is supported by skin tests, particularly patch tests containing the substances suspected of causing the hypersensitivity reaction.
Diagnostic tests:
Intraepidermal skin tests:
These are allergy tests, such as skin tests or RAST (Radioallergosorbent Test) tests, used to identify specific triggers, particularly in patients with systemic allergies or atopy, or in patients with a persistent course of the disease.
Conjunctival examination:
These involve conjunctival scrapings and the taking of biopsy samples. Giemsa-stained conjunctival scrapings may indicate the presence of an allergic reaction, as eosinophils and eosinophil granules are not normally present in the human conjunctiva.
Conjunctival provocation tests:
Conjunctival provocation tests may be performed using dry allergens or allergens in solution placed in the inferior conjunctival sac, or via contact lenses saturated with the allergen and placed on the cornea. In this way, the response can be observed clinically, and tears and conjunctival scrapings can be examined to assess the cellular response and the mediators released.
Tear assessment:
A cytological examination of the tear fluid reveals the presence of neutrophils, lymphocytes, and particularly eosinophils in the tear fluid, suggesting an allergic process. By studying the inflammatory mediators, a specific diagnosis of the type of ocular allergy can be reached.
Treatment
The main aim of treatment is:
To minimise and control the symptoms and signs of the allergic process, thereby improving the patient’s quality of life and breaking and preventing the cycle of ocular inflammation caused by prolonged exposure to allergens, which leads to the symptoms becoming chronic.
Allergen Avoidance and Control Measures
In the patient’s home, and particularly in the bedroom, it is advisable to avoid or remove items that accumulate large amounts of dust or dust mites, such as: carpets, rugs, curtains, cushions, bookshelves, soft toys or excessive and unnecessary ornaments, as well as pot plants.
Likewise, special attention should be paid to the bed, avoiding pillows and duvets filled with bird feathers (goose).
It is recommended that you replace your mattress when it is worn out, or cover it with a fully sealed synthetic or linen cover to prevent dust mites from spreading.
Windows or doors leading outside should remain closed in adverse environmental conditions (wind, dust, pollution, pollen season and flowering periods). Likewise, the filters in central air conditioning systems, mini-split units or window units should be cleaned or replaced frequently. Air filters designed to trap microparticles are useful at night whilst the patient is sleeping.
Furthermore, close contact with pets such as cats, dogs and birds should be avoided.
Outdoors, protective glasses with UV filters should be worn, particularly on windy days or in very dusty environments.
- Do not rub the eyes, as this can worsen the itching.
- Practise eyelid hygiene using sterile wipes.
- Reduce exposure to allergens.
Artificial Tears
They dilute and wash away allergens and chemical mediators from the ocular surface, whilst also providing a barrier effect that prevents the allergen from interacting with antigen-presenting cells in the conjunctiva.
It is advisable to apply them cold (they should be stored in the fridge) to help reduce itchy eyes, and relatively frequently during the acute stages of the allergic process.
When avoidance and limitation of allergen exposure, along with physical measures, fail to relieve symptoms, it is necessary to administer pharmacological agents that counteract the allergic process:
Vasoconstrictors and decongestants:
Vasoconstrictors are very effective in reducing conjunctival hyperaemia due to their alpha-adrenergic effect, although their action is very short-lived (2–4 hours).
Non-steroidal anti-inflammatory drugs:
They could be used as adjunctive treatments to reduce itchy eyes and conjunctival redness in acute cases that are difficult to control, particularly ketorolac.
Systemic antihistamines:
Useful in patients with seasonal allergic conjunctivitis accompanied by upper respiratory tract symptoms and bronchial asthma, and in patients with atopic keratoconjunctivitis, particularly if they suffer from atopic dermatitis.
Single-action topical antihistamines:
They act more rapidly than oral antihistamines and have a better safety profile. They do not cause significant systemic adverse effects and generally do not contribute to dry eye. They are not recommended for angle-closure glaucoma.
Single-action mast cell stabilisers:
They work by stabilising the mast cell basement membrane (affecting activation and degranulation), preventing the release of histamine and other pro-inflammatory substances, and reducing the influx of inflammatory cells such as eosinophils, neutrophils and monocytes.
Topical corticosteroids:
These are the most potent pharmacological agents in the management of all forms of ocular allergy in both the acute and chronic phases. They have immunosuppressive and antiproliferative properties. Their potential adverse effects are a drawback: delayed healing, increased susceptibility to infection, elevated intraocular pressure and the formation of cataracts. For this reason, they should only be used for short periods (1–2 weeks); if used for longer periods, close monitoring is required for the development of ocular hypertension, glaucoma or cataracts.
Other types of allergies
Giant Papillary Conjunctivitis
This condition occurs in genetically susceptible individuals and is associated with the use of contact lenses, particularly soft lenses, ocular prostheses, and sutures or their remnants. It can occur at any age, with no preference for race or gender, and may affect patients with or without a history of allergies, although symptoms are usually more severe in atopic patients. A predisposing factor is dry eye syndrome.
In Giant Papillary Conjunctivitis, there is eye irritation that worsens as the day progresses with contact lens wear, red eye, a foreign body sensation, blurred and fluctuating vision associated with blinking and vertical displacement of the lens when blinking, tearing, abundant and sticky mucous discharge in the mornings, and an urgent need to remove the contact lens to find relief.
The main clinical feature is the presence of giant papillae (>1 mm in diameter) on the upper eyelid conjunctiva. Unlike the vernal form, the papillae are more regular and uniform, with rounded tips and a more even distribution across the anterior and middle regions of the upper tarsus. The cornea is either minimally or not affected.>
Atopic Keratoconjunctivitis
This is the most severe form of ocular allergy. It is most common in adults aged between 20 and 50, particularly men, the majority of whom have a personal or family history of major allergies, primarily atopic dermatitis (95% of cases), as well as rhinitis and bronchial asthma in 87% of patients.
Atopic Keratoconjunctivitis is a chronic, recurrent condition affecting the surface of the eye and the eyelids, which can lead to serious visual complications due to fibrosis and scarring.
It is considered the ocular counterpart of atopic dermatitis, and there are frequently eczematous lesions on the skin of the eyelids or elsewhere on the body; these are erythematous and raised, taking the form of very itchy, scaly plaques, usually located in the antecubital and popliteal regions.
Ocular symptoms are characterised by periods of redness and intense eye itching, accompanied by tearing, photophobia, a burning sensation, a foreign body sensation, mucous discharge and blurred vision.
Chronic eyelid oedema causes a double fold in the infraorbital skin (Dennie-Morgan’s fold) and, due to intense scratching in the periocular area, loss of the tail of the eyebrow may be observed (Hertoghe’s sign).
Contact Dermatoconjunctivitis
It is caused by direct contact between the skin of the eyelids or the conjunctiva and a sensitising agent such as make-up, cream, sun cream, lotion or any other chemical substance, via the hands or other means. It can occur in anyone, even those with no history of allergies. In people who have already been sensitised, the immune response takes 48 to 72 hours to manifest following exposure to the allergen.
Contact Dermatoconjunctivitis is a form of contact dermatitis in which the inflammatory process affects the skin of the eyelids and the conjunctiva, as well as the external ocular surface. One or two days after applying the sensitiser, the skin of the eyelids becomes red and moderate itching develops. The bulbar and lower eyelid conjunctiva are subsequently affected, showing hyperaemia and chemosis, before the condition spreads to the eyelids, causing oedema and erythema, and to the rest of the conjunctiva.
25% of the population (children and adults) may be affected by this condition, which is frequently associated with allergic rhinitis (inflammation of the nasal mucosa).
The best way to prevent the symptoms of allergic conjunctivitis is to minimise or avoid contact with the allergen.
Below are a number of tips to alleviate symptoms or prevent them from occurring: