This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Conjunctiva, Subject name: Ophthalmology
Phlycten is due to- 
Select and explain. 
A. Exogenous allergy, B. Endogeneous allergy, C. Viral Keratitis, D. Fubgal keratitis
B: Endogeneous allergy
Answer: B: Endogeneous allergy 
Explanation: Phlyctenular keratoconjunctivitis is a characteristic nodular affection occurring as an allergic response of the conjunctival and corneal epithelium to some endogenous allergens to which they have become sensitized. Phlyctenular conjunctivitis is of worldwide distribution. However, its incidence is higher in developing countries. ref: A K KHURANA OPHTALMOLOGY,E4, Page-77