Thanks, keep smilin....

I got the impression this was a rash, not bites or separate lesions. But people vary in the use of terms for skin conditions.
For instance shingles may look like a rash at times, but other times there are just discreet vesicles. They don't itch tho, and mostly hurt.

I am familiar with the posts here on skin lesions, and discoloration.

But it is always a good idea to rule out something on top of the RSD... especially here where the severe itching and spreading was so quickly manifesting.

Some rashes hurt (I've had photosensivity reactions on my arms that burned like the devil). But a very itchy rash, can be many things and mostly dealt with if the right doctor looks at it.

Taking a picture and posting can help with this.
There are also viral exanthems but they don't itch as a rule.