Welcome back to Just Answer. Where is the tail red and swollen? How long has it been like this?
Ok. With that history, your girl could be having allergies. Allergies can be due to something in the environment or due to something being eaten.
Here are two good links on the allergies.Airborne allergies:http://www.VeterinaryPartner.com/Content.plx?P=A&S=0&C=0&A=597Food allergies:http://www.VeterinaryPartner.com/Content.plx?P=A&S=0&C=0&A=652
At this point in time, there could also be a secondary skin infection going on to compound the discomfort / ichiness.
My best recommendation is to get to your vet to have them evaluate the skin in those areas and then the best medications can be started up. At home, diphenhydramine (benadryl) is something that can provide relief with some. Here is a link going over its use.