Why does my dog have bumps all over his body?

Sounds like allergy.

It's my very strong belief that we overvaccinate dogs. If you google for Dr. Ron Schultz, he's a veterinary immunologist who has been saying this for decades. Basically, annual vaccines are a revenue source. Some vets are very defensive on this topic. Some will admit it. Some will say it's a "lessor of two evils" dilemma (dog owners won't bring dogs in for annual checkups without the "magical" booster requirement). I think that latter excuse has merit. But, it also involves a conflict of interest. The vet makes money on the "magic" stuff, and also when the dog owner returns after some years for allergy treatments (after the immune system is battered by unnecessary immunizations).

If it's your dog, try to find a naturopathic/holistic vet. Look for one who's really into it, lives/breathes it. Not just someone trying to tap into that market. I never believed in this stuff. But, I've seen two very serious skin problems completely resolved using natural practices (when traditional vets said my dog would be on lifetime allergy medicines, antibiotics, etc.). An alternative-practice vet will also be able to give you a different perspective on the industry practice of overvaccinating. They'll over titer testing (which is more normal in other countries). They'll recommend raw/fresh feeding. I supplement kibble with raw/fresh. (I did raw/fresh entirely for awhile 20 years ago. It's a lot of work. I think supplementing works almost as well, with much less effort.).

Good luck.

There are very few surprises that will startle you more than discovering a lump or bump on your dog. As your hand wanders over your canine pal in affectionate scratching or petting, your fingers just may chance upon a lump that “was not there before."  Keep in mind that not all lumps and bumps are cancerous, and some are fairly innocent and do not warrant immediate surgery but that is for your vet to determine