Which of the following OTC products' mechanism of action has noncompetitive H1-receptor antagonist and mast cell stabilizer properties?

A. Naphazoline/pheniramine: This combination includes a vasoconstrictor (naphazoline) and an H1 antihistamine (pheniramine) that competitively blocks histamine receptors. It does not provide mast cell stabilization, so it lacks the dual mechanism described. B. Ketotifen: Ketotifen is a noncompetitive H1-receptor antagonist with additional mast cell stabilizing properties. It prevents the release of histamine and other inflammatory mediators, making it effective for allergic conjunctivitis and fitting both mechanisms in the question. C. Tetrahydrozoline: Tetrahydrozoline is a topical ocular decongestant that works as an alpha-adrenergic agonist causing vasoconstriction. It reduces redness but has no antihistamine or mast cell stabilizing effects. D. Phenylephrine: Phenylephrine is also an alpha-adrenergic agonist that causes vasoconstriction in nasal and ocular tissues. It does not act on histamine receptors or stabilize mast cells, so it does not meet the criteria described.