Frenchie with bumps

Question
I have a 1yr old frenchie male, brindle, named Barnie. He is on the same food he has been for the 8 months I have had him, Natures Recipe chicken and pumpkin, grain free. He is using TropiClean hypo allergenic dog shampoo for sensitive skin. He gets two Canine Carry Outs each morning.

For the last month or so, he has started getting these raised bumps from the back of his neck to his little piggy tail. None on his underside, at all, none on his head, legs or feet. They don't itch, they aren't red, just raised very noticeable bumps.

I have taken him to the vet, who said it's normal and put him on antibiotics "just to be sure". They went away for a few weeks, but he is now covered down his back with them again. The vet mentioned steroids, but if they don't itch, crack, or weep I'm not sure why I would load him on prednisone. A few people have told me to give him regular Benadryl in small doses, but at 25 lbs, no one has told be what the "safe" dose is  to see if that works.

I'm looking for ideas on what this is, how to help treat it, and what to do. While it doesn't seem to bother him, it looks just awful and I don't want it to be some underlying issue that my vet might be missing.

Answer
If the antibiotics seemed to help relieve these bumps, then it could be something like a food allergy, so a strict hypoallergenic diet would be recommended. These could also be hives from an allergic reaction.  If the benadryl helps, then use it.  Prednisone for a short period of time may also help the allergy and if there are side effects, there are other steroids that may be better suited to your dog.  Another type of drug is called Atopica, which is not a steroid.