Most people get allergic conjunctivitis when their eyes come into contact with an allergen - a substance which makes the body's immune system overreact.
The eye becomes sore, inflamed and sometimes painful. Symptoms occur because the overreacting immune system makes the body release histamine and other active substances by mast cells - these cause dilation of blood vessels (blood vessels expand, widen), which irritates the nerve endings and causes increased secretion of tears.
Allergic conjunctivitis is not the same as infective conjunctivitis, the causes are different.
The following allergens are commonly found to cause allergic conjunctivitis:
- Pollen (hay fever)
- Animal fur
- Eye drops
- Dust mites.
Types of allergic conjunctivitis
Allergic conjunctivitis is usually broken down into different categories. Below are some of them:
1) Seasonal allergic conjunctivitis (allergic rhinoconjunctivitis)
Pollen is a common cause of allergic conjunctivitis
Pollen is the most common allergen to cause conjunctivitis in countries that have cold winters (not near the equator).
If you get conjunctivitis from pollen you will probably have symptoms of hay fever, which includes sneezing, blocked or runny nose, itchy nose, and itchy and watery eyes. When the conjunctivitis occurs along with sneezing and blocked nose, etc., the whole thing is called hay fever.
This type of conjunctivitis is called seasonal allergic conjunctivitis (allergic rhinoconjunctivitis) because it almost exclusively occurs during the spring and summer months when plants, especially grass, trees, and flowers are in pollen. Some people even have symptoms during early autumn (fall).
2) Contact conjunctivitis (Contact dermatoconjunctivtis)
These are usually caused by make-up (cosmetics), eye-drops or other chemical which irritate the conjunctiva of sensitive people, causing an allergic response. Some people are sensitive to specific substances.
Symptoms usually develop two to four days after the substance comes into contact with the eyes.
3) Giant papillary conjunctivitis
This is generally caused by contact lenses. When sensitive people put the contacted lenses on they cause discomfort - this can get progressively worse and more and more uncomfortable, causing the eyes to become red.
Giant papillary conjunctivitis (GPC) may also occur after eye surgery when the patient uses hard contact lenses.
Some people say that poor hygiene when handling contact lenses, solutions and cases may contribute to infections of the eye.
4) Perennial (all year round) conjunctivitis
As the name suggest, this type of conjunctivitis persists throughout the year. It is mainly due to an allergy to house dust mites - microscopic insect-like creatures that live mainly in bedding, upholstered furniture and carpets. Dust mites eat skin cells shed by people - they love warm, humid environments. Dust mite allergy is an immune system response to a specific dust mite protein, causing other problems as well as conjunctivitis, such as blocked/runny nose, sneezing, and contraction of the airways (asthma).
Other causes may be animal dander (small scales from animal skins or hair or bird feathers that can cause allergic reactions in some people).
Symptoms of allergic conjunctivitis
Most people with allergic conjunctivitis have problems with both eyes. Symptoms may appear quickly, soon after the eyes have come into contact with the allergen. In other cases, as with some eye drops, symptoms may take from two to four days to appear.
The following symptoms are most typical for allergic conjunctivitis:
Pink/red eye is a common symptom of conjunctivitis.
- Eyes become red/pink - by far the most common symptom. The eyes become irritated as the capillaries (small blood vessels) in the conjunctiva widen.
- Pain - some people have pain in one or both eyes. If the eyes are very red and painful it is important to see a doctor. Any patient with painful, red eyes, and has become sensitive to light (photophobia), and feels his/her vision is affected should see a doctor straight away.
- Itchiness - as the eyes are irritated they may itch. The itch may worsen if you keep rubbing them.
- Swollen eyelids - the eyelids may puff up when the conjunctiva becomes inflamed, or if the sufferer has been rubbing them a lot.
- Soreness - the inflammation may make the whole area feel sore and tender. Some people say the soreness feels like burning.
People with seasonal allergic conjunctivitis will experience symptoms at certain times during the year - usually from early spring, into summer, and even into autumn (fall). Those with perennial allergic conjunctivitis are susceptible at any time of year, and may find certain times of the day are worse than others.
If the eyelids are red, cracked and/or dry it is an indication that the patient most likely has contact conjunctivitis. Contact conjunctivitis and giant papillary conjunctivitis are not seasonal - symptoms may occur at any time of year.
Diagnosis of allergic conjunctivitis
A good GP (general practitioner, primary care physician) should be able to diagnose allergic conjunctivitis by examining the patient and assessing signs and symptoms. Signs are what the doctor can see (e.g. red eye), symptoms are what the patient describes to the doctor (e.g. pain). The doctor will ask about other symptoms, such as sneezing and blocked/runny nose.
The GP will also need to rule out any other conditions which present similar symptoms.
If you experience the following symptoms you should see a doctor immediately - it is possible that you may have a more serious condition:
- Painful eyes
- Sensitivity to light (photophobia)
- Vision problems
- Very red eyes.
The following conditions, apart from allergic conjunctivitis, may also cause reddening of the eyes:
- Infective conjunctivitis - caused by bacteria or a virus, or a sexually transmitted disease (an infection).
- Acute glaucoma - an unusual form of glaucoma which causes a build up of pressure in the eye. Symptoms can appear rapidly. Untreated, acute glaucoma can cause incurable vision loss.
- Keratisitis - the cornea becomes inflamed, and occasionally ulcerated. Sometimes it can progress to scarring of the cornea, resulting in permanent vision loss.
- Iritis - inflammation of the iris. If left untreated the iris may stick to the lens, preventing vital fluid drainage from the pupil. The result could be irreversible eye damage.
The doctor will also check whether some object or substance, like an eyelash, may be causing the irritation.
Severe cases - if symptoms are very severe, or worsening, the GP may refer the patient to an eye specialist (ophthalmologist).
Recent surgery - anyone who has had recent eye surgery and develops papillary conjunctivitis will be referred to an ophthalmologist by his/her GP. It is vital that the eye(s) is carefully monitored and that treatment be effective. Most GPs will also send the patient to an ophthalmologist if dermatoconjunctivitis is suspected - the aim here is to get the diagnosis confirmed.
Treatments for allergic conjunctivitis
Whatever the cause of the conjunctivitis may be, the following may help:
- Contact lenses - do not wear them until symptoms have cleared up completely. If you have used any medication on the eye(s), wait 24 hours after treatment has ended before wearing contact lenses.
- Rubbing the eyes - the less you rub your eyes the better. Rubbing the eyes may cause the inflammation to get worse. This is easier said than done - itchy eyes makes you want to rub them.
- Bathing the eyes - use a flannel soaked in cold water. Some people say that immersing their face in clean warm water and opening the eyes help - others most definitely do not.
- Avoid the allergen - if pollen levels are high stay indoors and close all windows. If you go out wear a wrap around your glasses or sunglasses. If your pillows have feathers, consider changing them for materials you know you are not allergic to. Steps to lower the number of dust mites in the home can sometimes control dust mite allergy.
Patients seeking fast relief from symptoms often benefit by taking antihistamines. In cases of allergic conjunctivitis the doctor may advise an oral presentation, or eye drops. Antihistamines basically block the effects of histamines which are produced by the body when the immune system reacts to a foreign substance. One could say that an antihistamine makes your immune system less aggressive.
The most commonly prescribed oral histamines for allergic conjunctivitis are cetirizine, fexofenadine and loratadine - these are usually taken once a day.
The most commonly prescribed antihistamine eye drops include azelastine, emedastine and ketoifen. They are applied to the eyes twice or three times a day.
Most people say antihistamines reduce allergic conjunctivitis symptoms considerably, as well as other symptoms, such as runny nose, blocked nose, itchy nose, and sneezing. Some antihistamines may cause drowsiness. People taking antihistamines for the first time should refrain from driving or operating heavy machinery until they know whether or not the medication affects them.
Mast cell stabilizers
Mast cell stabilizers take much longer to start having any beneficial effects, compared to antihistamines - but when they start working, their effects last much longer. Some patients are given an antihistamine at the same time so that there is some relief of symptoms before the mast cell stabilizers kick in. The most popular mast cell stabilizers are lodoxamide and nedocromil. They are presented as eye drops.
A mast cell stabilizer is a class of non-steroid controller medicine that reduces the release of inflammation-causing chemicals from mast cells. They block a calcium channel essential for mast cell degranulation, stabilizing the cell; thus preventing the release of histamine.
These are only prescribed if symptoms are especially severe. They are rarely prescribed. Corticoid is a steroid hormone produced by the adrenal cortex. As medication, corticosteroids are produced synthetically - they reduce swelling and decrease the body's immune response.
Corticosteroids work well but should not be used long-term because of possible side effects.
Complications of allergic conjunctivitis
Complications of perennial or seasonal allergic conjunctivitis are extremely rare. More of a frustration, than a complication, is the recurrence of symptoms. People with pollen allergies may become annoyed with the annual ordeal.
Allergic conjunctivitis is unpleasant. It can disrupt the smooth running of day-to-day life. Concentration may be affected, especially if symptoms are in the eyes - visual data is crucial for concentration. Experts say that allergic conjunctivitis should have no long-term impact on the sufferer's health.
Complications of dermatoconjunctivitis and giant papillary conjunctivitis
There is a bigger chance of complications with these two types of conjunctivitis. Even though the risk is greater, it is still small.
There is a risk that the cornea may become inflamed (keratitis). Keratitis can cause ulcers to form on the cornea, significantly raising the risk of scarring, which can cause permanent impairment of vision. Symptoms of keratitis are:
- Intense pain in the eye
- Sensitivity to light (photophobia)
- Blurred vision
- A feeling that there is something in the eye
- Watery eyes.