My teenage daughter has had a swollen left upper eyelid for over a month. slight puffiness below the eye also. no other symptoms. ?

Puffy: This could be a longstanding chalazion, an inflammation of one or more oil glands in the eyelid. Try some warm compresses for a few days and see if the puffiness declines. If not, call your local eye doctor for an appointment.

Time for visit: The persistence of swelling in this area for a month is likely due to chronic irritation of the tear glands. If you've tried warm compresses for a while & this persists it may be time for you to see an eye doctor. Occasionally this can persist for months & only resolve if the glands are opened from the inside of the eyelid & shelled out.