Hello, Thank you for your query. Insect bites, foreign objects, injury, starting of an infection and as you rightly suspected, allergies can all cause eye swelling. -does she have any pain? -is the white of her eye reddened? -does she have a cold? Or had a recent cold? -any possibility of dust or other particles in eye (playing in the sand or traveling near an open window, for instance)? It may take a while for discharge to occur if it is an Infection. I recommend : - cool compresses -clean eye with a clean wash cloth if discharge occurs -wash eyes with boiled and cooled water. Water should go into the eye. You could also pour this water over her face while she keeps her eye open as much as possible (you would need lots more water for this) -apply lubricant eye drops (maybe be available as an OTC) if her eye feels itchy or dry. Avoid putting any object in to the eye or applying pressure with fingers. Washing the eye should remove any particles lodged in. If it does not get better in a day or if she develops pain and discharge, see an ophthalmologist for professional help. Patch her eye with a clean cloth or cotton (make sure it doesn t press against her eye, it should only protect the eye). Hope this helps. Please let me know if there is anything else I can help you with. Wish you both good health.