Sounds like an allergy to a group of preservatives ending in zolinone. The most famous being methylisothiazolinone. These preservatives can be in shampoos (even anti dandruff head and shoulders), conditioners, shower gels, deodorants, hand wash, cleaning products, washing detergents, fabric softeners, sun cream, washing up liquid (even fairy liquid), hand creams, moisturisers and even in paints and wallpaper paste. It is a very common allergy affecting at least 10% of the population. This preservative can be added to products that it wasn’t previously in so you may suddenly find you are allergic to something you weren’t before.
Does look like allergic reaction benedril might help.
If your insurance pays you could see virtual or teledoc cheap.
Clothes detergent does this to me we use All free and clear. Any food allergys like strawberries.
Avoid all berries. Elimination diet could help
Has your husband changed his job or come into contact with something different at work? Paint,dust,chemical etc.
Do you have a new pet or has he touched any animals?
Do you have any new plants indoors or near where you live?
Is he under any stress or worried about anything?
Any bereavement lately?
All these things can cause a sudden rash as well as the other things mentioned by Moon and Gunga.
Get him to take an antihistamine tablet one per day for 2 weeks as well as applying the itch cream
He hasn’t experienced any of those changes that could be allergens (new job, pet, foods, etc) the only thing different is he got new work shirts that he didn’t wash the first time he wore them (they were new and not worn by anyone else prior) but we’ve washed them several times since then. Hasn’t been under any stress. He’s been taking antihistamines regularly for the itch as well as tried several itch creams (including the female yeast infection creams because someone recommended trying lol) nothing has improved it. We don’t have insurance until April when his work insurance will start. He works at a factory making car parts not like around any chemicals and has worked there for 7 months. He’s still visited our primary care doctor and the doctor didn’t seem to have any knowledge of what it could be. I’m going to send you a private message!
here’s another picture from today. I tried to upload one of his whole back which is covered, but the file size is too big.