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Diagnosing allergic conjunctivitis

NHS ChoicesMedical Reference

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There is no procedure or test to confirm allergic conjunctivitis. Your GP will usually be able to make a diagnosis by assessing your symptoms and examining your eyes. If you have allergic conjunctivitis, you will usually have itchy and inflamed (swollen) eyes.

Your GP will also ask about any other symptoms that you may have. For example, if you have allergic conjunctivitis that is caused by pollen, you may also have a runny nose or be sneezing a lot.

Your symptoms can be easily confused with a different type of conjunctivitis, such as irritant or infective conjunctivitis. These have different causes and will be treated differently. In most cases, describing how your conjunctivitis started will indicate to your GP which type of conjunctivitis you have:

  • Irritant conjunctivitis is caused by an irritant, such as an eyelash getting into your eye. 
  • Infective conjunctivitis is caused by an infection, for example after being in close contact with someone who is infected.
  • Allergic conjunctivitis is caused by an allergen (a substance that you are allergic too, such as pollen).

Other conditions

If you have any unusual symptoms (see Symptoms of allergic conjunctivitis), such as severe pain or sensitivity to light, you may have a different eye condition. In this case, it is very important to seek medical assistance immediately, either by contacting your GP or visiting your nearest accident and emergency (A&E) department.

If you experience unusual or severe symptoms, they may be a sign of a more serious condition. Your GP will need to rule out these conditions as part of your diagnosis, otherwise they may cause complications.

Other eye conditions that you may have include:

  • acute glaucoma: a rare form of  glaucoma (an eye condition that affects your vision) and causes a painful build-up of pressure in your eye
  • keratitis: where your cornea (the clear layer at the front of the eye) becomes inflamed (swollen), leading to the formation of ulcers (open sores)
  • iritis: a type of  uveitis (inflammation of the middle layer of your eye) that causes pain, headaches and watery eyes


If your conjunctivitis symptoms are severe or get worse, your GP may refer you to an ophthalmologist (a specialist in eye conditions).



Allergy is the term used to describe an adverse (bad) reaction that the body has to a particular substance.


An allergen is a substance that reacts with the body's immune system and causes an allergic reaction.


Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.
Medical Review: March 05, 2010

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