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. Fungal keratitis
B: Endogeneous allergy
Answer: B: Endogeneous allergy 
Explanation: Phlyctenular conjunctivitis - Endogenous allergy It is believed to be a delayed hypersensitivity (Type IV cell mediated) response to endogenous microbial proteins. Causative allergens are :- (i) Staphylococcus proteins (most common); (ii) Tuberculous proteins and (iii) Proteins of Moraxells axenfeld bacillus and ceain parasistes. Vernal keratoconjunctivitis - Exogneous allergy Reference : AK khurana 7th edition