Some medicines make you feel light-headed, or like your head is in the clouds, or make it hard to think clearly. This feeling is described as being "out of it."
Jim, are you okay? You look really out of it!
Yeah, I just took some allergy medicine and it leaves me feelign this way. But the hives were worse!
No for me. I'd rather itch then feel like I had a head full of cotton!.