Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
Is soft region fluidy, warm, or sore to the touch?
Where on the neck is it located (ie under/attached to the jaw, lower, etc)?
Any recent traumas or wounds in this area?
How much Benadryl did you give? How often? How much does Bella weigh?
Has it reduced at all after that dose?
Can you take a photo of this? If you can do so and post them online, it will let me see what you are seeing. To post them, you can either use the paperclip on the tool bar. Or if you cannot see that on your phone/computer, then you can post them on any site (ie Flickr, Photobucket, Imgr etc) and paste the web address here for me to have a peek.