Yesterday, I asked: Can antihihistamine Eye Drops, enter your system through your eyes? While the question seems somewhat idiotic, I am highly allergic to antihistamines. They knock me out for extended periods of time, by making me lethargic, and extremely drowsy and sluggish. I used an antihistamine eye drop yesterday, and, shortly, had all the above symptoms. My question is simply, can one's system absorb antihistamines through the use of antihistamine eye drops?