Hi there and thanks for your question.
Although I can't see your dog, I can picture exactly what you are describing. The brownish red staining that you are describing comes from her saliva. When we see it it is a clue that tells us that the dog has been licking excessively at a certain area.
The most common reason for excessive licking of the paws is allergy. While food allergy is possible, the most common type of allergy is to environmental elements such as weeds or grasses. Some dogs with allergies respond to Benadryl, but most of them need a small dose of steroids to get good relief.
Allergies can cause some redness and licking around the anus. But, if the saliva staining is around her vulva, then this would make me more suspicious about a bacterial vaginal infection.
It does sound like she should see a vet. If you would like to look into using Benadryl you can read about that here:
http://www.petplace.com/drug-library/diphenhydramine-benadryl/page1.aspx
But, if there is a bacterial infection, then the sooner we get this dealt with the better! Unfortunately there is no effective over the counter medicine for bacterial infections.
I hope she does ok!
I hope this information helps! I will be online for a short while more. So, if you have more concerns about this question you can just hit reply. However, my baby will be waking up from her nap soon and I will be offline after that. If that happens I will respond when I come online again. Or, if my answer has been sufficient, please hit accept. Thanks!
Dr. Marie.
The above is given for information only. Although I am a licensed veterinarian, I cannot legally prescribe medicines or diagnose your pet's condition without performing a physical exam. If you have concerns about your pet I would highly advise contacting your regular veterinarian.
Veterinarian
Compassionate licensed veterinarian with >20 years experience with cats, dogs and pocket pets