Patient information: Allergic conjunctivitis (Beyond the Basics)


Conjunctivitis, also called "pink eye," is defined as an inflammation of the conjunctiva. The conjunctiva is the thin membrane that lines the inner surface of the eyelids and the whites of the eyes (called the sclera) (figure 1). Conjunctivitis can affect children and adults. The most common symptoms of conjunctivitis include a red eye and discharge.

There are many potential causes of conjunctivitis, including bacterial or viral infections and allergies. All types of conjunctivitis cause a red eye, although not everyone with a red eye has conjunctivitis. The term “pink eye” refers primarily to conjunctivitis caused by viruses (such as adenoviruses), rather than other causes. Therefore, this term should not be used when the underlying cause of the conjunctivitis is unknown or is not thought to be viral.

This topic review discusses the signs and symptoms, evaluation, and treatment of allergic conjunctivitis. Other types of conjunctivitis are discussed separately. (See "Patient information: Conjunctivitis (pinkeye) (Beyond the Basics)".)


Allergic conjunctivitis is caused by airborne allergens that come in contact with the eye. Symptoms may be sudden in onset (acute), seasonal, or present year-round (perennial), depending upon the allergen.

Acute allergic conjunctivitis — Acute allergic conjunctivitis is a sudden-onset reaction that occurs when a person comes in contact with a known allergen, such as cat dander. Symptoms include intense episodes of itching, redness, tearing, and swelling of the eyelid. Symptoms can be severe, although they usually resolve within 24 hours of removal of the allergen.

Seasonal allergic conjunctivitis — Seasonal allergic conjunctivitis (SAC) is a form of eye allergy that usually causes milder but more persistent symptoms during a particular pollen season(s).

Seasonal allergens include tree pollens in the spring, grass pollens in the summer, and weed pollens in the late summer and fall, although there is some variation based upon geographic location (figure 2).

Perennial allergic conjunctivitis — Perennial allergic conjunctivitis (PAC) is a mild, chronic, allergic conjunctivitis related to year-round environmental, usually indoor, allergens such as dust mites, animal danders, and molds.


The most common symptoms of allergic conjunctivitis include redness, watery discharge, and itching of both eyes. Other symptoms can include burning, sensitivity to light, and swelling of the eyelids. Both eyes are usually affected, although symptoms may be worse in one eye. Rubbing the eyes can worsen symptoms.

People with allergic conjunctivitis often have a history of other allergic conditions, such as eczema, seasonal allergies, or a specific allergy (eg, to cats).


There are a number of treatments available for the symptoms of allergic conjunctivitis. In addition, basic eye care is important.

Basic eye care

  • Avoid rubbing the eyes. If itching is bothersome, use artificial tears, a cool compress, or antihistamine eye drops (see 'Medications' below).
  • Minimize exposure to pollen by staying inside when possible, using air conditioning, and keeping car and home windows closed during the peak allergy seasons (figure 2). (See "Patient information: Allergic rhinitis (seasonal allergies) (Beyond the Basics)".)
  • People with year round allergic conjunctivitis should consider consulting an allergy specialist to determine which allergens are responsible for their symptoms (eg, dust mites, cat dander, others).

  • People with sudden-onset symptoms can use a combination antihistamine/vasoconstrictor eye drop four times daily for up to two weeks. These are available without a prescription.
  • People with seasonal or year round symptoms are usually treated with a combination antihistamine/mast cell stabilizer eye drop. Most of these require a prescription. Ketotifen is an eye drop in this category that is available without a prescription.
  • An oral antihistamine may be most helpful when it is taken preventively (before symptoms develop). However, antihistamines may also be used to treat symptoms after they have started, although the greatest benefit may not be seen for several days.

    Non-sedating oral antihistamines include fexofenadine (generic, Allegra®), loratadine (generic, Claritin®), desloratadine (Clarinex®), cetirizine (generic, Zyrtec®), and levocetirizine (Xyzal®). Loratadine and cetirizine are available in the United States without a prescription.

    Diphenhydramine (Benadryl®) is a short-acting, sedating antihistamine that can be taken at bedtime to reduce night-time itching.

If symptoms of allergic conjunctivitis do not improve after two to three weeks of the above treatments, the person should see an ophthalmologist for evaluation.

Treat dry eyes — People with allergic conjunctivitis often produce an inadequate amount of tears, which can cause dryness of the eye. This can worsen symptoms of allergic conjunctivitis. However, it is not always possible to know if a person has inadequate tear production unless an eye examination is performed.

If inadequate tear production is diagnosed, treatment often includes use of a lubricant eye drop or ointment. These products are available without a prescription in most pharmacies. Preservative-free preparations are more expensive and are necessary only for people with a severe case of dry eye and those who are allergic to preservatives.

Lubricant drops can be used as often as hourly with no side effects. The ointment provides longer lasting relief but blurs vision temporarily. For this reason, some people use ointment only at bedtime. It may be worthwhile to switch brands if one brand of drop or ointment is irritating, since each preparation contains different active and inactive ingredients and preservatives.


Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site ( Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

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Patient information: Conjunctivitis (pinkeye) (The Basics)
Patient information: Seasonal allergies (The Basics)
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Patient information: Conjunctivitis (pinkeye) (Beyond the Basics)
Patient information: Allergic rhinitis (seasonal allergies) (Beyond the Basics)

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Allergic conjunctivitis
Evaluation of the red eye

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