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Allergic conjunctivitis (red eye; pink eye)

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What is Allergic Conjunctivitis (Red Eye; Pink Eye)

Conjunctivitis is a very common reason for an individual to experience an uncomfortable, red eye. There are several causes of conjunctivitis, including bacteria, viruses and, importantly, allergies.

Allergic conjunctivitis affects the conjunctiva of the eye. The conjunctiva refers to the thin, translucent lining of the eyeball and the undersurface of the eyelids.

Anatomy of the eye: Click here to view larger image

There are several different types of allergic conjunctivitis, including:

  • Simple allergic conjunctivitis (SAC);
  • Vernal keratoconjunctivitis (VKC);
  • Atopic keratoconjunctivitis (AKC); and
  • Giant papillary conjunctivitis (GPC).

In allergic conjunctivitis, the conjunctiva becomes inflamed due to allergic reactions, also known as hypersensitivity reactions.

There are several different types of hypersensitivity reactions. Simple allergic conjunctivitis (SAC) is mediated by a Type 1 (immediate) hypersensitivity reaction. This reaction triggers the release of a number of chemicals from mast and other cells, and the migration of more cells to the site of the reaction.

Other forms of allergic conjunctivitis, such as VKC, AKC and GPC, are caused by a combination of Type 1 and other types of hypersenstivity reactions.

Simple allergic conjunctivitis (SAC)

SAC refers to both seasonal allergic conjunctivitis (SAC) and perennial allergic conjunctivitis (PAC).

Simple allergic conjunctivitis For more information, see Simple Allergic Conjunctivitis.

Vernal keratoconjunctivitis (VKC)

Vernal keratoconjunctivitis (VKC) represents a more chronic and severe form of allergic conjunctivitis, strongly linked to a personal or family history of other allergic (atopic) diseases.

Atopic keratoconjunctivitis (AKC)

Atopic keratoconjunctivitis (AKC) refers to inflammation of the conjunctiva and eyelids. It usually occurs in both eyes and is strongly linked to atopic dermatitis (a type of eczema).

Giant papillary conjunctivitis (GPC)

Giant papillary conjunctivitis (GPC) refers to a conjunctival reaction to prolonged irritation caused by a foreign body. Most commonly the foreign body causing this irritation is contact lenses. GPC is not always considered to be classically allergic in origin.

For more information, see Giant papillary conjunctivitis (GPC)

Statistics on Allergic Conjunctivitis (Red Eye; Pink Eye)

Allergic conjunctivitis (of any type) is extremely common, affecting up to 40% of the population. There is some suggestion that allergic conjunctivitis is becoming more common, perhaps due to increasing air pollution and cigarette smoking.

Risk Factors for Allergic Conjunctivitis (Red Eye; Pink Eye)

There are a number of factors that may make someone more likely to develop allergic conjunctivitis, although these vary depending on the specific type of conjunctivitis.

Family and personal histories are important factors in all types of allergic conjunctivitis. A personal or family history of allergic disease, including hayfever (allergic rhinitis), asthma or atopic dermatitis (eczema) increases the risk of an individual developing allergic conjunctivitis.

Other predisposing factors for allergic conjunctivitis include the environment, age, gender, and the condition of the eyes.

Progression of Allergic Conjunctivitis (Red Eye; Pink Eye)

The course of allergic conjunctivitis is variable. In simple allergic conjunctivitis (SAC), the condition is often self-limiting, although it may be more long-term in some cases. In other types of allergic conjunctivitis, the condition often improves as an individual grows older.

Complications can occur in some cases if left untreated, so it is always important to seek your doctor’s advice.

Symptoms of Allergic Conjunctivitis (Red Eye; Pink Eye)

Allergic conjunctivitisAnyone with eye symptoms should visit their doctor and provide a detailed clinical history. This is necessary to rule out other, more serious, conditions that can cause uncomfortable red eyes. It also helps to rule out other causes of conjunctivitis, as the treatment and management varies between these.

If you have eye symptoms or signs, your doctor will pay close attention to several aspects of your clinical history. In particular, they may ask:

  • Have you had recent exposure to other people with conjunctivitis or an upper respiratory tract infection? This may suggest a viral cause of conjunctivitis.
  • What are the details of your sexual history? In particular, have you had Chlamydia or Gonorrhoea? These can both cause conjunctival eye disease.
  • Are you using any prescription or over-the-counter medications? Some medications can produce an in inflammatory reaction.
  • Have you previously had any eye diseases, used contact lenses, or had any other conditions that can be associated with eye conditions (e.g. rheumatoid arthritis)?
  • Do you have a family history of atopic (allergic) conditions, such as allergic rhinitis (hayfever), asthma or dermatitis (eczema)?

People affected by allergic conjunctivitis generally have a specific set of eye symptoms, including:

  • Itching;
  • Tearing with a watery discharge;
  • Burning;
  • Stinging; and
  • Mild sensitivity to light (photophobia).

The most common symptom experienced in allergic conjunctivitis is itching. If you have a red eye without itchiness, you may have a different eye condition. If this is the case, it is extremely important to seek medical advice from a doctor as soon as possible.

The itching caused by allergic conjunctivitis is usually mild. Some people may experience intense and intolerable itching, although this is less common. The eyes are generally uncomfortable, but are not normally painful. You may experience worse symptoms with warmer weather, and some people find that nasal symptoms (e.g. itchy or runny nose) accompany their eye symptoms.

If you experience severe, continuous eye pain and reduced vision, it is very important that you seek the advice of a doctor, and you may need urgent referral to an ophthalmologist. These features are not typically present in allergic conjunctivitis and may point to a more serious eye condition.

Clinical Examination of Allergic Conjunctivitis (Red Eye; Pink Eye)

OphthalmoscopeThe doctor will begin by looking at the external eye and eyelids for any signs of eyelid involvement such as dermatitis. To examine the conjunctiva, the doctor may need to retract or evert the eyelid. This is a painless, though slightly uncomfortable, process. The doctor will ask you to look down, while a cotton swab (Q-tip) is placed horizontally on the upper eyelid. The doctor will then gently grasp the upper lid eyelashes and pull the eyelid out and up, gently rolling it over the cotton swab to see the under-surface of your eyelid.

The doctor may use an ophthalmoscope to view the back of your eye. The doctor may also use a slit-lamp microscope to see the front structures of your eye. Both of these are painless, routine examinations.

How is Allergic Conjunctivitis (Red Eye; Pink Eye) Diagnosed?

Often investigations are not required, because allergic conjunctivitis can be diagnosed with the clinical history and examination.

Some additional tests that may help to establish the diagnosis and provide further information about the condition include testing of the tears, skin allergy testing, and conjunctival scraping.

Conjunctival scraping is done to examine conjunctival cells under a microscope. The doctor performing this will explain the test carefully and use some eye drops to make your eye less sensitive to touch. A sample of cells is then gently obtained from the inner surface of the eyelid. This procedure may be slightly uncomfortable, but should not be painful.

Prognosis of Allergic Conjunctivitis (Red Eye; Pink Eye)

In many cases, the symptoms of allergic conjunctivitis are mild, long-term treatment is not needed, and the prognosis is favourable. In more complicated cases, the prognosis depends on the type of allergic conjunctivitis and the specific treatments available.

How is Allergic Conjunctivitis (Red Eye; Pink Eye) Treated?

Non-pharmacological therapy

Allergic conjunctivitisThere are many options for people experiencing the signs and symptoms of allergic conjunctivitis. Some people find that using a cool compress over the area, or controlling their house’s climate with air-conditioning, can help. Both of these strategies are particularly helpful in cases of allergic conjunctivitis that are made worse by warmer environments.

Try to avoid rubbing or touching your eyes, as eye-rubbing may result in more inflammation. Some people also find it helpful to use eye lubricants and refrigerating eye drops.

Pharmacological therapy

There are a number of different medications that can be used for allergic conjunctivitis. The exact treatment plan will depend on the type of conjunctivitis you have and how severe your symptoms are. In many cases, your immediate symptoms will be controlled with a short-term treatment program, followed by a more long-term maintenance plan.

If you find your symptoms are not improving or are getting worse despite treatment, you should return to your doctor as soon as possible for a review.


The symptoms of allergic conjunctivitis arise because the chemicals released in response to the allergic trigger prompt a number of changes and inflammation. The small blood vessels in the eye enlarge, contributing to the redness, itchiness and discomfort experienced.

Decongestants are a type of medication available as an eye drop. They keep the small blood vessels constricted, and so may provide some relief from allergic conjunctivitis. Side effects can occur if these are over-used or are used for a long time, so you should use them according to your doctor’s instructions.


Many of the symptoms in allergic conjunctivitis are due to histamine. Histamine is released by cells in response to an allergic trigger, and causes itching, enlargement of the blood vessels and a number of other inflammatory changes.

Short-term relief of the itching and redness can be provided by topical antihistamines and vasoconstricting eye drops. Antihistamine agents attach to the same cells in your body as histamine, and in doing so prevent histamine from attaching to these cells. This minimises some of the effects of histamine, thereby reducing the itchiness, redness and discomfort associated with allergic conjunctivitis. Antihistamine agents are most effective in milder cases of allergic conjunctivitis.

Mast cell

Mast cells play a central role in allergic conjunctivitis, and most mild to moderate forms of allergic conjunctivitis are now treated with mast cell stabilisers. They prevent mast cells from opening up and releasing histamine and other chemicals that produce the symptoms of allergic conjunctivitis. They do not relieve the immediate symptoms, but avoid further episodes of allergic conjunctivitis. Mast cell stabilisers are effective in most people and are generally safe, but like all medications they should only be used according to your doctor’s advice.

NSAIDs (non-steroidal anti-inflammatory drugs)

Allergic conjunctivitisTopical NSAIDs may be considered in some cases of allergic conjunctivitis, as they reduce itchiness and redness. NSAIDs do this by blocking enzymes involved in producing the chemicals that contribute to allergy and inflammation. Significant side effects can occur with NSAID use, so keep your doctor updated on how your treatment is progressing.

Topical or systemic corticosteroids

In severe cases of allergic conjunctivitis, steroid eye drops may be used, but these should be used very carefully. They should only be used for 1–2 weeks, under supervision of an ophthalmologist and with regular review, due to the possible side effects including glaucoma, cataracts and corneal infections. Corticosteroids are not recommended in all people with allergic conjunctivitis, but are important in the treatment of some subtypes.

Topical or systemic cyclosporin

Another type of drug that may be helpful for some people with allergic conjunctivitis are immunomodulating drugs such as cyclosporin. Cyclosporin attaches itself to certain cells in the body, known as T-lymphocytes. By binding to these cells, cyclosporin prevents the production of chemicals involved in inflammation and therefore reduces inflammatory and allergic symptoms. These are powerful medications and should be used with caution and only following the instructions of your doctor due to potential side effects.


Immunotherapy involves giving slowly increasing doses of a specific allergen to a sensitised individual, with the aim to increase their tolerance towards that allergen. Immunotherapy for allergic conjunctivitis has been shown to have a beneficial effect on allergic eye symptoms in some people. However, it is not yet clear how long the effect lasts and whether it is better to give immunotherapy under the tongue (sublingually) or in the skin (subcutaneously.) The effects of immunotherapy on allergic eye symptoms are still being researched and studied.

More information

Allergic conjunctivitis For more information about allergic conjunctivitis and its subtypes, see Allergic Conjunctivitis.

Allergic Conjunctivitis (Red Eye; Pink Eye) Prevention

People who know what causes their allergic conjunctivitis can help prevent the condition by avoiding their triggers. Allergic triggers can be avoided by:

  • Using sunglasses to act as a barrier for airborne allergens;
  • Using hypoallergenic bedding;
  • Washing sheets in hot water; and
  • Minimising animal exposure, if animals are believed to trigger allergic symptoms.

People who do not know what causes their allergic conjunctivitis may consider consulting an allergy specialist. The specialist may do allergy testing to identify factors that trigger the symptoms.

Allergic Conjunctivitis (Red Eye; Pink Eye) References

  1. Khaw PT, Shah P, Elkington AR. ABC of Eyes (4th edition). London: BMJ Publishing Group; 2004.
  2. Leibowitz HM. The red eye. N Engl J Med. 2000;343(5):345-51.
  3. Bielory L, Friedlaender MH. Allergic conjunctivitis. Immunol Allergy Clin North Am. 2008;28(1):43-58.
  4. Khurana AK. Comprehensive Ophthalmology (4th edition). New Delhi: New Age International Publishers; 2007.
  5. Schmid KL, Schmid LM. Ocular allergy: Causes and therapeutic options. Clin Exp Optom. 2000;83(5):257-270.
  6. Singh K, Bielory L. Ocular allergy: A national epidemiologic study. J Allergy Clin Immunol. 2007; 119(1 Suppl): S154.
  7. Bonini S. Atopic keratoconjunctivitis. Allergy. 2004;59 Suppl 78:71-3.
  8. Ono SJ, Abelson MB. Allergic conjunctivitis: Update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol. 2005;115(1):118-22.
  9. Abelson MB, Granet D. Ocular allergy in pediatric practice. Curr Allergy Asthma Rep. 2006;6(4):306-11.
  10. Moloney G, McCluskey PJ. Classifying and managing allergic conjunctivitis. Medicine Today. 2007; 8(11): 16-21.
  11. Bielory L, Mongia A. Current opinion of immunotherapy for ocular allergy. Curr Opin Allergy Clin Immunol. 2002;2(5):447-52.
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Posted On: 8 October, 2005
Modified On: 15 May, 2018
Reviewed On: 2 August, 2010


Created by: myVMC