You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Spring catarrah is - and explain in detail?
It is considered a hypersensitivity reaction to some exogenous allergen, such as grass pollens. VKC is thought to be an atopic allergic disorder in many cases, in which IgE-mediated mechanisms play an impoant role. Such patients may give personal or family history of other atopic diseases such as hay fever, asthma, or eczema and their peripheral blood shows eosinophilia and inceased serum IgE levels. Ref: A K KHURANA COMPREHENSIVE OPHTALMOLOGY,E4,page-74