5yo/f no allergies/sensitivities but very swollen eyes in winter. dr has no idea. sleeping well & in excellent health?

Possible dryness?: Have you considered just plain old dryness that causes irritation of her eyes just in the winter? I would try saline drops during the day and applying a saline gel at bedtime and see if that solves the problem. If forced air heat in your house, I'd also invest in getting the ductwork professionally cleaned. You wouldn't believe what can hide in old ducts!