8 year old daughter had red and swollen eye lid, 24 hours now. no redness in actual eye, no pus, no itchy/grainy feeling, no pain. what could it be?

Could be many things: See your eye doctor urgently! If it's swollen for no reason that's not normal. You want to make sure there is no cellulitis developing or worse. Just because there's no itching or pain means it's not an allergy response, but doesn't exclude other causes. Don't delay! We only have 2 eyes. Want to make sure her intraocular pressure is safe too. She needs an eye exam!

Periorbital swelling: While it's reassuring that there is no pain, it is still concerning for periorbital cellulitis - an infection of the tissue around the eye. This needs to be evaluated and likely need antibiotics. Get her into her pediatrician ASAP. If her doc doesn't have weekend hours then go to an urgent care or ED for evaluation.