I have this exact same problem with my dog. She's a black lab about 2 years old. She will secreat a very pungant liquid every once in a while. I took her in to have her anal sacs examined, one was full, but the liquid was clean, no infections. She doesn't scoot, or wimper or anything. Last night she was asleep on the couch, and when she woke up she started licking the base of her tail. Call me crazy, but she seemed embarassed. I went to examin her and she didn't want me touching her tail. I did get a hold of her to examin the area, she didn't struggle, so actually lifting her tail didn't bother her, she's just very skidish.
My question is what can I do to remedy the situation? I've heard its diet related, is that true? Any help would be greatly appreciated.