It sounds like your dog is having an allergic reaction, and has hives. He may have been stung, or bitten by something.
Try using Benedryl.
Stick with plain benadryl tablets (benadryl without added decongestant). The correct dosage is 1 mg per pound of the dog's body weight.
Benedryl is very common, and you should be able to purchase it easily, even at this time of night. Try a grocery store, a super mart, an all night pharmacy, or even a gas/convenience store. The bumps should start to disappear within an hour of giving the medication. You can give him another dose 6 hours later. If the hives do not go away, or if they do, but then comeback...You need to get him to the vet.
If at anytime, your dog is drooling, having trouble breathing,or if any area of his neck or head starts to swell, you need to get him to the vet ASAP.
If he starts to get hives on a regular basis, you will need to find out what he is allergic to.
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