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Phlyctenular conjunctivitis is a classic hypersensitivity reaction associated with primary tuberculosis (TB). This condition arises due to the immune response elicited by Mycobacterium tuberculosis, particularly when there is an involvement of the ocular tissues. In primary tuberculosis, delayed-type hypersensitivity (type IV hypersensitivity) can lead to the formation of a phlyctenule, which is a raised, pink, and ulcerated area on the conjunctiva or cornea. This reaction occurs as a result of the immune system recognizing the antigens present in the bacteria, leading to localized inflammation.

The other options presented do not directly reflect the classic hypersensitivity reaction to primary TB. A negative TST (tuberculin skin test) would indicate a lack of sensitization, which is not indicative of an active hypersensitivity reaction. While cutaneous rashes and skin lesions can occur in various allergic reactions or inflammatory processes, they are not specifically associated with primary tuberculosis as phlyctenular conjunctivitis is. Thus, the select choice effectively highlights a specific and classic manifestation of hypersensitivity within the context of primary tuberculosis infection.