Seasonal / perennial allergic conjunctivitis (SAC / PAC) is a common cause of ocular irritation and itching that is noninfectious. Allergens can be seasonal, such as pollen and ragweed, or nonseasonal, such as dust, eye drops, mold, or cosmetics. The process is an immunoglobulin E (IgE)-mediated hypersensitivity reaction, and a personal or family history of atopy is common.

Typical symptoms of allergic conjunctivitis include swollen eyelids, mucoid discharge, and intense ocular itching. Itching is the most commonly reported symptom, and patients may also complain of a feeling of dirt or sand in the eyes. At times, the edema of the eyelids can be quite severe and be associated with scaling and fissure formation of the periocular skin.

Atopic keratoconjunctivitis (AKC), giant papillary conjunctivitis (GPC), and limbal and tarsal vernal keratoconjunctivitis (VKC) are rarer, more severe forms of allergic conjunctivitis. Although GPC may be recurrent, it does not carry as great a risk of long-term corneal damage and vision loss as AKC and VKC. People with other forms of atopic disease are more likely to develop AKC or VKC, often associated with atopic dermatitis and allergic rhinitis, respectively. Some of these forms of allergic conjunctivitis are discussed in more detail elsewhere; this writeup will focus on seasonal and perennial disease.