I took my Mable to the vet once when, cleaning under her tail (she had no pocket - Like Bo) I saw blood on the babywipe. I freaked. It was clear from her behavior that it was sore. I was a new EB person then and had NO IDEA the path I was about to embark upon....LOL Anyway, turns out, it was dry and cracked under there. Ouch. Bo's tail care includes frequent wipes (ok, scrubbin') with the baby wipe under there (One and Done, Huggies Cucumber and Aloe) and either Desitin or Hydrocortisone cream in the area where tail meets bottom.
Bea's cavernous tail pocket (I swear, I hear an echo when I speak into it) is another post all together. LOL