Wow he is Handsome.
It's hard to tell from the pictures, they could be hives but it could also be a reaction to something like mosquito bites, gnats or even ant bites if he got in to an ant hill. In some cases a bacterial staph infection can cause this as well.
If he is itchy lets go ahead and treat this like an allergic reaction. You can use the Benadryl. This is dosed at 1-2 mgs per pound of body weight. In cases like this what we would do is give this at 2mgs per pound for the 1st and 2nd dose. This can be given every 8 hours. Drop down to the 1mg per pound for the 3rd and additional doses. Use this for 3 days.
If he is reacting to the new laundry soap we have to remember he could react to everything that was washed with that including your clothing.
If he does not clear up after 3 days of Benadryl, gets more bumps or is so itchy that he is uncomfortable I would have him seen by a vet. It is possible he may need stronger medication such as steroids or an antibiotic if he has developed a bacterial infection.
I hope this helps give you some direction and he feels better soon.
Please reply back if you have additional questions and I will be happy to continue.
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