What is allergic conjunctivitis?
Allergic conjunctivitis is an inflammation inside the eyelids and on the surface of the eye (conjunctiva) that happens as a result of allergy (sensitization of the immune system to a certain natural protein).
It is difficult to estimate how many patients are affected as the symptoms are often under-appreciated, and many patients go without seeking medical care. Simple ocular allergy likely affects between 10% to 30% of the general population. In most cases, onset occurs in patients younger than 20 years old with decreasing prevalence in older populations. Allergic conjunctivitis can be seen as an isolated finding but is often associated with allergic rhinitis, atopic dermatitis, and/or asthma.
What are the types of allergic conjunctivitis?
Allergic conjunctivitis is classified by the time symptoms continue.
Acute allergic conjunctivitis
Symptoms might start dramatically fast and be gone. This type of reaction is called acute allergic conjunctivitis. Usually it is an immediate exposure to sensitizing allergen that you came in direct contact with. For example, such reaction can happen in a classroom if a child is allergic to a cat, and other students who have cats brought the allergen on their clothes.
Chronic allergic conjunctivitis
If the eye itching and redness continues for a long time such condition is called chronic allergic conjunctivitis. The problem may be seasonal (March – July for grasses) or year-round (dust mite allergy). Just as the timing of exposure becomes constant, the conjunctivitis may become a chronic problem if not treated correctly.
What causes allergic conjunctivitis?
Simple allergic conjunctivitis (acute, seasonal and perennial) is an immunoglobulin E (IgE) mediated hypersensitivity reaction (type I) and resultant mast cell degranulation secondary to direct contact with an allergen to the ocular surface. As such, there is an immediate and delayed phase of the reaction mediated by different inflammatory modulators.
Who is at risk for allergic conjunctivitis?
Nowadays allergy and atopy is very common. So, anyone who has allergy may develop allergic conjunctivitis. Why in some people eyes are affected by allergic reaction, while other suffer from asthma or sinusitis? No one really knows. It must be somehow explained by the genetic differences, but to this day this question remains unanswered.
What are the symptoms of allergic conjunctivitis?
Allergic conjunctivitis rarely comes alone. It also affects both eyes at the same time. In certain cases, people notice that they will start having symptoms after petting a cat or a dog, or holding Guinea pig. Others will have eye symptoms in the middle of a grass season.
Independent of what actually causes allergy, the symptoms are very similar:
- Itchy eyes
- Red eyes
- Goopy discharge on the eyelids and eyelashes, gluing the eyelids together
While lurry vision may be due to viscous eye discharge clouding the visual acuity, true vision problems should alert you that other problems may be happening. We recommend to go to the optometrist or ophthalmologist right away if there is significant pain, vision changes, or if all the symptoms are happening only in one eye.
Other allergic symptoms are frequently coexisting with conjunctivitis:
- Swelling and redness of the eyelids
- Atopic eczema
- Runny, congested nose
- Postnasal drip
- Cough and wheezing
- Headache, irritability
- Inability to concentrate
How is allergic conjunctivitis diagnosed?
The diagnosis is made clinically with a thorough history and classic physical examination findings. If there is any concern based on the history and physical examination, fluorescein staining of the cornea can be used to ensure that there is no corneal abrasion.
Laboratory testing is generally not needed, although skin prick or serum allergy testing can be helpful for mitigating the disease process by identifying the offending allergens so that they can be avoided if possible.
While allergic conjunctivitis is known to cause severe symptoms, people rarely develop complications. One of the most frequent problems is a secondary infection due to rubbing and mucus accumulation. Corneal ulcers and cataracts are among significant but rare conditions associated with allergic conjunctivitis.
How is allergic conjunctivitis treated?
Patients should be assessed for any atopic conditions, such as asthma or eczema, and for symptoms that indicate impaired quality of life, such as poor sleep, daytime somnolence, or irritability. Prevention involves allergen avoidance and environmental controls.
Oral antihistamines, intranasal steroids, or intranasal antihistamines are the first line of treatments used for nasal and ocular symptoms.
Patients also benefit from allergy skin testing and allergen immunotherapy with SLIT or allergy shots.
Home care. Most of the time uncomplicated allergic conjunctivitis is not even a reason to see a doctor. If you find what exactly caused the problem, you can eliminate symptoms by avoiding the exposure.
First aid if you or your child suddenly has itchy eyes:
- Wash the hands and face with plenty of water
- Splash cold water in the eyes
- See what is in immediate contact (petting a cat, or smelling a flower bush)
Later on, when you visit an allergist it is important to give the right history of exposure.
If reaction happens again, or if it continues despite first measures, you may want to try taking OTC medications that have anti-allergy effect. We highly discourage using medications that have decongestants – these have no effect on the allergic conjunctivitis, but may cause headaches and habitual use.
Antihistamine eye drops are fast-acting and safe for management of ocular symptoms; intranasal antihistamines are effective for nasal symptoms. Oral antihistamines should be used if many allergic symptoms are present. We recommend modern non-drowsy antihistamines that cause less slipiness and are safe if you drive the car. Remember – first generation antihistamines such as Benadryl and atarax do inhibit your reaction and can cause car accidents.
Mast cell stabilizers
Mast-cell stabilizers inhibit the release of histamine from mast cells. These therapeutic agents prevent the mast-cell degranulation process and eventually inhibit the inflammatory cascade in allergic conjunctivitis. These agents are effective in both acute and chronic allergic disorders, exhibit fewer local or systemic side effects then steroidal medications.
- Sodium cromoglycate is the oldest therapeutic agent. It acts by inhibiting secretion of mast cells. The action of this drug is concentration dependent. Sodium cromoglycate in combination with steroids or oral histamine is more effective and reduces the dose.
- Nedocromil sodium, exerts its effect by inhibiting chloride channel in mast cells, which in turn reduces histamine release.
- Pemirolast potassium 0.1% ophthalmic solution is used to alleviate the signs and symptoms associated with seasonal allergic conjunctivitis. Pemirolast potassium is a more potent mast cell stabilizer than cromolyn sodium and tranilast. It acts by inhibiting type I immediate hypersensitivity reaction.
- Lodoxamide is approximately 2500 times more potent than sodium cromoglycate in different animal models. It inhibits both acute and chronic phase response by blocking histamine release from mast cells and eosinophil chemotaxis. Lodoxamide 0.1% ophthalmic solution is indicated in the treatment of vernal conjunctivitis and keratoconjunctivitis.
Current guidelines recommend against combining intranasal steroids and oral antihistamines, as this provides no additional benefit. Oral steroids are last resort in severe reaction, and should not be recommended with allergic conjunctivitis as a solo presentation of the allergy.
How do I prevent allergic conjunctivitis?
As any allergy, allergic conjunctivitis can be prevented by maintaining good health of the immune system – healthy lifestyle, good amount of exercise and outdoor activity, organic healthy food and allergen control of the indoor environment.