What is the cause of vaginal itching with no other symptoms?

Vaginal itch: It could be something as simple as a new soap, detergent or fabric softener or feminine hygiene product. If no discharge - i would see if there is any new products you are using - anything that may have come in contact down there could cause itching. If its external - Benadryl (diphenhydramine) cream might help - if internal - a simple vinegar and water douche might help.