Allergic conjunctivitis: An in-depth guide with practical information
Allergic conjunctivitis is a condition that occurs when the conjunctiva (an almost transparent membrane that covers the white part of the eye, the sclera, and also the eyelids on the inner side) become inflamed as a consequence of an excessive reaction of the immune system (in response to an external agent). Its function is to protect the eyeball from external agents, although it is also involved in forming tear components and the eye's immunological defense.
Going more into scientific concepts, we should mention that allergic conjunctivitis is due to a type I hypersensitivity reaction to a specific antigen.
It is essential to know that there is not only one type of this condition, but there are several manifestations, each of which will be explained in detail below, as well as its manifestations and treatments.
In most cases, seasonal allergic conjunctivitis (hay fever conjunctivitis) tends to peak in spring, late summer, or early autumn and disappears during the winter months, depending on the life cycle of the plant responsible.
Ocular pruritus is the most frequent symptom (particularly intense in the nasal quadrant of the eye), together with conjunctival hyperemia. There may also be foreign body sensations, burning, and tearing. The discharge is watery at first, becoming serous and thicker in chronic forms; the eyelids and conjunctiva are usually involved, with varying degrees of chemosis (gram blister appearance).
The palpebral conjunctiva usually has a pale pink or milky appearance (related to edema); corneal involvement is less frequent, although punctate epithelial keratitis may be found. Unlike other ocular diseases, it is rarely followed by permanent visual impairment.
Among the most frequent causal agents are tree, grass, and weed pollens that present a botanical periodicity.
It is usually a type 1 hypersensitivity reaction (IgE-mediated) triggered by aeroallergens that bind to mast cells upon binding to their IgE receptors, causing their degranulation with subsequent release of cytokines and other inflammatory mediators.
The reactions produced can be divided into an early phase lasting 20 to 30 minutes, which is related to the specific activation of conjunctival mast cells, causing their degranulation, releasing histamine, proteoglycans, proteases (tryptase, chymase), acid hydrolases and oxidizing enzymes, as well as de novo formation of lipid mediators (prostaglandins and leukotrienes), platelet-activating factor, interleukins (IL4, IL5, IL6, IL8, IL13) and tumor necrosis factor-alpha (TNF-α). After that, this reaction follows a late phase caused by stimulation of epithelial cells and fibroblasts with the release of proinflammatory cytokines and chemokines and characterized by infiltration of inflammatory cells (neutrophils, eosinophils, lymphocytes, and macrophages), with subsequent persistent conjunctival inflammation; unlike other allergic diseases, there is little eosinophilic infiltration in acute forms, which increases as the pathology becomes chronic.
Perennial allergic conjunctivitis (PAC)
Perennial allergic conjunctivitis (PAC) (atopic conjunctivitis, atopic keratoconjunctivitis) is mainly caused by dust mites, animal dander, or other non-seasonal allergens. These allergens, especially in domestic environments, cause symptoms throughout the year.
Symptoms are persistent and may be exacerbated both seasonally (79% of cases) and by non-specific irritants, and there may be some cases associated with occupational exposures, such as in flower growers.
PAC may be more likely to cause chronic inflammation than seasonal due to the prolonged nature of the exposure.
Vernal keratoconjunctivitis (VKC)
On the other hand, vernal keratoconjunctivitis (VKC) is a more severe type of conjunctivitis, more likely allergic in origin. It is common in males between 5 and 20 years of age with a history of eczema, asthma, or seasonal allergies. Vernal keratoconjunctivitis typically recurs each spring and subsides in the fall and winter. Many children outgrow the disease in early adulthood.
This is characterized by a chronic bilateral and recurrent inflammation, whose predominant symptom is usually intense itching, to which are added hyperemia, edema, photophobia, foreign body sensation, lacrimation, and the production of a whitish and fibrous secretion composed of eosinophils, epithelial cells, and Charcot-Leyden crystals. The symptoms are usually exacerbated by exposure to wind, dust, solid lights, or physical exertion with sweating.
This condition mainly has two forms of conjunctival involvement: tarsal and limbar. The first is related to the presence of giant papillae (7-8 mm) that primarily affect the upper tarsal conjunctiva and give it a characteristic cobblestone appearance. In the limbus, Horner-Trantas spots can be found, which are observed as small gelatinous nodules, are typical of the active phase of the disease, usually last from 2 to 7 days, and are caused by the accumulation of eosinophils and epithelial cell detritus.
It should be noted that giant papillae present in the tarsal conjunctiva cause mechanical damage and corneal involvement in 5% of patients; in these cases, micropannus (vascularization of the cornea as a result of repeated inflammation), superficial punctate keratopathy (punctate epithelial denudation usually located in the upper half of the cornea), corneal macroerosions and ulcerations can be observed. In persistent forms, subepithelial fibrosis is generally found, appearing as a linear whitish scar parallel to the lid margin (Arlt's line) and pseudogerontoxon (opacification of the cornea adjacent to the upper limbus).
It is necessary to mention that histopathologically, VKC corresponds to both a type I and type IV hypersensitivity mechanism. Conjunctival biopsy reveals increased basophils, eosinophils, degranulated mast cells, plasma cells, and lymphocytes. Tears show high levels of histamine, tryptase, eotaxin, eosinophil cationic protein, major essential protein, adhesion molecules (VCAM-1), leukotrienes (LTB4, LTC4), IgE and IgG specific for aeroallergens and eosinophils in 90% of cases, supporting both a Th1 and Th2 response.
Although it can be self-diagnosed by signs and symptoms, it is important to treat in time for possible refractive pathologies it might cause in children.
Now, one of the main symptoms is ocular pruritus (itching); that is why we must treat our children immediately to avoid the response that is caused, which is rubbing since it can cause a mild to severe "astigmatism" when performing this act.
On the other hand, not having control over how to treat the symptoms can trigger a thinning of the cornea, which leads to a dreaded "keratoconus" (conical shape of the cornea), producing irregular and diminished vision at an early age.
In case of the appearance of symptoms compatible with allergic conjunctivitis (red eye, tearing, itching, foreign body sensation, mucous secretion, egg white appearance...), it is necessary to visit a specialist for its timely diagnosis and treatment.
The initial treatment consists of attenuating the symptoms and periodic control with the specialist.
Let us remember that prevention is the basis of medicine, leading us to avoid serious complications.
- Over-the-counter topical antihistamines, nonsteroidal anti-inflammatory drugs, mast cell stabilizers, or a combination of these.
- Topical corticosteroids or cyclosporine for treatment-resistant cases. Sometimes oral antihistamines.
- Avoiding identified allergens and using cold compresses and artificial tears can reduce the symptoms of allergic conjunctivitis; antigen desensitization is sometimes helpful.
- Over-the-counter antihistamine eye drops (e.g., ketotifen) may be effective in mild cases. When these drugs are insufficient, prescription antihistamine eye drops (e.g., olopatadine, bepotastine, azelastine, cetirizine), mast cell stabilizers (e.g., nedocromil, cromoglycate), or nonsteroidal anti-inflammatory drugs (e.g., ketorolac) may be used separately or in combination.
- Topical corticosteroids (e.g., loteprednol eye drops, 0.1% fluorometholone, 0.12-1% prednisolone acetate in drops three times daily) may be helpful in treatment-resistant cases or when rapid relief of symptoms is of interest. Because topical corticosteroids can cause an outbreak of latent ocular herpes simplex virus infections, with a risk of ulceration and perforation and, in prolonged use, glaucoma and cataracts, their administration should be initiated and supervised by an ophthalmologist.
- Topical cyclosporine drops may be helpful. Corticosteroid ointment or tacrolimus applied to the skin is very effective in treating atopic dermatitis of the eyelids.
- Oral antihistamines (e.g., fexofenadine, cetirizine, or hydroxyzine) may be helpful, especially when patients experience other allergic symptoms (e.g., rhinorrhea).
Seasonal allergic conjunctivitis does not usually require drug combinations or intermittent topical corticosteroids.
Dr. Glaybeth Lara Hidalgo
Who are the top experts researching treatments for allergic conjunctivitis?
The top experts researching allergic conjunctivitis are: Hiroshi Fujishima, Leonard Bielory and Andrea A Leonardi.
What are the top concepts researched in studies about allergic conjunctivitis?
The most researched concepts in studies of allergic conjunctivitis are: allergic conjunctivitis, allergic conjunctivitis asthma, allergic conjunctivitis mice, allergic conjunctivitis vkc and allergic conjunctivitis eczema.
What are some of the top places that specialize in allergic conjunctivitis?
Recommended institutions that specialize in allergic conjunctivitis:
- London Medical TestingUniversity House, 11-13, Unit 12 Lower Grosvenor Pl, London SW1W 0EX, United Kingdom Phone: +447883375180
- Saurabh Jain, Consultant Ophthalmic Surgeon2nd Floor, 215 Great Portland St, London W1W 5PN, United Kingdom Phone: +447938561892
- James Chodosh, M.D., MPH243 Charles St, Boston, MA 02114 Phone: +16175733938
Recent articles about Allergic Conjunctivitis
Relationship Between Refraction And Allergic Conjunctivitis
.. and allergic conjunctivitis in order to reveal possible insights into the pathogenesis in 1015 subjects.MethodsThe patients were divided into four groups: contact lens wearers with ...
Known for Allergic Conjunctivitis | Refractive Error | Factor Pathogenesis | Investigated Relationship
Immune Regulatory Mechanisms In Allergic Conjunctivitis: Insights From Mouse Models
.. of allergic conjunctivitis. Mouse models have facilitated prospective studies that have not been possible in patients. The availability of gene knockout mice and the wealth of monoclonal ...
Known for Allergic Conjunctivitis | Mouse Models | Regulatory Cells | Phase Reaction | Animal Humans
Specific Ige In Tear Fluid And Features Of Allergic Conjunctivitis
.. for allergic conjunctivitis, but it is still unclear whether the measurement of tear fluid IgE is helpful for assessing the severity of allergic conjunctivitis. In this study, we evaluated ...
Known for Allergic Conjunctivitis | Tear Fluid | Specific Ige | Immunoglobulin Male | Severity Score
Update And Clinical Utility Of Alcaftadine Ophthalmic Solution 0.25% In The...
.. have allergic conjunctivitis, and as such, it is the most common form of ocular allergy. Seasonal allergic conjunctivitis is the most prevalent type of allergic conjunctivitis that impacts ...
Known for Allergic Conjunctivitis | Ocular Allergy | Ophthalmic Solution | Mast Cell | Hyperemia Tearing
Changes In Tear Function And The Ocular Surface After Topical Olopatadine...
.. with allergic conjunctivitis and to analyze the effect of topical olopatadine treatment on corneal sensitivity, tear function, and impression cytology variables.
METHODS: This was a ...
Known for Allergic Conjunctivitis | Ocular Surface | Topical Olopatadine | Tear Function | Goblet Cells
Role Of Histamine H4 Receptor In Allergic Conjunctivitis In Mice
.. in allergic conjunctivitis. Histamine is the most important mediator in allergic conjunctivitis. We measured eye scratching behavior and allergic-like symptoms score, that is, hyperemia ...
Known for Allergic Conjunctivitis | Histamine H4 | Receptor Antagonist | Scratching Behavior | Protein Coupled
A New Murine Model Of Allergic Conjunctivitis And Effectiveness Of Nedocromil Sodium
.. BACKGROUND: Allergic conjunctivitis is the most common atopic disease affecting the eye. To study the pathophysiology and effectiveness of antiallergic drugs, it is necessary to develop ...
Known for Allergic Conjunctivitis | Murine Model | Nedocromil Sodium | Mast Cells | Clinical Signs
Γδ T Cells Are Required For Maximal Expression Of Allergic Conjunctivitis
.. in allergic conjunctivitis.
METHODS: Wild-type (WT) C57BL/6 and γδ T cell-deficient (TCR-δ(-/-)) mice were immunized intraperitoneally and challenged topically for 7 consecutive days with ...
Known for Allergic Conjunctivitis | Γδ Cells | Adoptive Transfer | Th2 Cytokines | Natural Killer
Measurement Of Interleukin-4 And Histamine In Superficial Cells Of Conjunctiva In...
.. during allergic conjunctivitis. Ten patients with cedar pollen-allergic conjunctivitis and 10 patients with postsurgical conjunctivitis were enrolled in this study. Cells were collected by ...
Known for Allergic Conjunctivitis | Brush Cytology | Il4 Histamine | 10 Patients | Conjunctival Cells
Clinical Correlations Of Dry Eye Syndrome And Allergic Conjunctivitis In Korean Children.
.. and allergic conjunctivitis were investigated.
METHODS: Children aged 6 to 15 years with dry eye symptoms were included. Slit-lamp examinations including tear film break-up time, ...
Known for Allergic Conjunctivitis | Dry Eye | Pediatric Patients | Subjective Symptoms | Tear Film