Atopic keratoconjunctivitis is one of four major ocular (eye) allergies that are closely related to one another. All four are associated with inflammation of the eyes and surrounding tissues, but each has their own distinguishing characteristics:

• Allergic rhinoconjunctivitis. Also known as “hay fever conjunctivitis,” or “allergic conjunctivitis,” it occurs when allergens such as pollen, mold, pet dander or dust mites trigger an allergic response that inflames the conjunctiva (a membrane that covers the white of the eye and inside of eyelids). Symptoms include itchiness, clear discharge and redness of the eye. Swelling of the surrounding tissues is also likely. This is usually diagnosed when symptoms appear in tandem with allergic rhinitis.
  
  
• Contact keratoconjunctivitis. A form of contact dermatitis that usually occurs when the eye reacts to an eyedrop, cosmetic or allergen transferred from the hand to the eye through rubbing or another action.
  
  
• Vernal conjunctivitis. A sight-threatening inflammation of the membrane covering the back of the eyelid (tarsal conjunctiva). It primarily affects children younger than 14, and at least twice as many boys as girls have the condition. Allergens that come into contact with the eye are believed to be at the root of the condition. It affects both eyes (bilateral) and occurs most often in hot, dry climates during the spring and summer. 

Atopic keratoconjunctivitis shares many characteristics with vernal conjunctivitis. However, there are some key differences:

* Gelatinous, white clumps of degenerated eosinophils
^ Proliferation of blood vessels in abnormal quality

Other related disorders include:

• Atopic dermatitis. A disorder of the upper layers of the skin that usually begins in childhood. It typically affects those in families with a history of atopic dermatitis, allergic conditions or asthma. Scaly, itchy skin rashes are typical symptoms of the disorder, which is the most severe and longest-lasting form of dermatitis. Atopic keratoconjunctivitis is associated with atopic dermatitis of the eyelid and face.
  
  
• Contact dermatitis. Any inflammation that occurs on the skin’s surface after coming into contact with an allergen or irritant. While uncomfortable, the condition is usually not serious, though it should not be left untreated. Contact dermatitis is the most common source of work–related diseases.
  

  

• Allergic rhinitis (hay fever). An inflammation of the inner lining of the nose that occurs when an allergic individual encounters an airborne allergen such as pollen, mold, dust mites or animal dander. Many people with atopic keratoconjunctivitis also suffer from allergic rhinitis.
  
  
• Asthma. A chronic inflammation of the body’s bronchial (airway) tissues that afflicts millions of people in the United States. An asthma attack occurs when exposure to allergens or other stimuli further inflame the airways, leading to an inability to expel trapped air from the lungs. Many people with atopic keratoconjunctivitis also suffer from asthma.