sounds like sun poisoning are you using sun block or sun screen cause there is a diff.
Since the rash is non itchy hence it looks less likely to be due to allergies. It looks like due to sun burns. Apply cool compresses on the area and take bath with cool(not very cold) water. Do not scrub your skin or shave your skin and use a soft towel and gently pat your skin dry.Also use a sunburn Over-The-Counter remedy containing aloe vera and a light moisturizer or a dusting powder to relieve chafing. You can apply silver sulfadiazine (1% cream) on the skin except face and see if it helps.If the symptoms still persist then you should consult a dermatologist .
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
I'm using sunblock. Its like they are blisters or pimples, they hurt but not itch. I have them in my neck and face everytime i go to the beach or am under the sun for a long period of time. I used sunblock #90. Its like my face and neck break out. If i leave my back uncovered I break out too.