In most cases, patients will report a history of seasonal or other allergies. Seasonal allergies typically produce a thin, watery discharge and do not involve the cornea. If the patient exhibits thick, ropy discharge with severe itching and corneal involvement, it is most likely VKC rather than a seasonal allergy. VKC's prevalence is higher in the warmer climates. Onset is typically between the ages of three and 25 years.
Males are typically more affected than females.
An allergic response is an unwarranted over-reaction of the body's immune system to foreign substances known as allergens, which the body wrongly perceives as a potential threat. The response can be innate or acquired. This discharges the pre-formed mediators. Their effects can be either direct, indirect or a combination of the two. Two important mediators released from mast cells, histamine and bradykinin, immediately begin to stimulate nerve endings called nociceptors, creating the sensation of itching.