<prompt> Phlycten is due to -Exogenous allergyEndogeneous allergyViral keratitisFungal keratitis  <response>: 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 