What is pink eye?

Conjunctivitis, also called pink eye, is an inflammation of the clear thin outer layer (conjunctiva) of the eyeball. When small blood vessels in the conjunctiva become inflamed, they’re more visible. This is what causes the whites of your eyes to appear reddish or pink.1 It can be caused by a virus, bacteria, an irritant (such as shampoo, smoke, or chlorine), or by allergies. When the inflammation is caused by a virus, bacteria, or irritant, it’s non-allergic conjunctivitis. When the inflammation is caused by allergies, it’s called allergic conjunctivitis. Allergic conjunctivitis can be caused by both seasonal and year-round allergies.   

Common Allergic Conjunctivitis Symptoms:

  • Itchy eyes and eyelids
  • Redness
  • Burning
  • Swollen eyelids
  • Blurred vision
  • Watery eyes

Non-allergic conjunctivitis can sometimes easily spread from person to person, but allergic conjunctivitis is not contagious.

Allergic Conjunctivitis

Allergic conjunctivitis differs from non-allergic conjunctivitis in a few ways:


Both eyes are usually affected (but may not be equally affected). 


Your eyes may water a lot, but they don't become gooey or sticky.


Nasal symptoms, such as sneezing and a runny nose, also known as rhinoconjunctivitis, often occur along with eye symptoms. 

Causes of Allergic Conjunctivitis

Allergic conjunctivitis can be caused by both year-round allergies and seasonal allergies. Seasonal allergic conjunctivitis usually happens during pollen season and is connected to allergic rhinitis symptoms. Eye inflammation that occurs year-round can be caused by:

Dust Mites

Allergic conjunctivitis can also happen as a reaction to things inserted in eyes, such as contact lens solutions and eye drops.


Why is testing important?

You may think your itchy eyes are a harmless nuisance, but it’s important to find out what’s causing it, i.e., the triggers. Living with conjunctivitis can have a negative impact on productivity and happiness at school and/or work.2 It’s important to determine whether your eye symptoms are caused by a virus or by allergies because each cause requires different treatments. And learning what may be behind your symptoms now could also help you avoid any potential vision problems in the future.

So how do you know if your symptoms are caused by an allergy? A simple blood test—together with your medical history—can help identify underlying allergen triggers, if you have an allergy. Knowing if you’re allergic and what you’re allergic to can help you or a loved one avoid or minimize symptoms. Be sure to consult with your healthcare professional.

Tools for Understanding Allergies


Track allergy symptoms and prepare for a visit with a healthcare provider.

Learn about specific allergens, including common symptoms, management, and relief. 

Are you a healthcare provider? Get comprehensive information on hundreds of whole allergens and allergen components.

  1. http://www.mayoclinic.org/diseases-conditions/pink-eye/basics/definition/con-20022732.
  2. Epling J. Bacterial conjunctivitis. BMJ Clinical Evidence. 2012;2012:0704.