Heat rash? Pic included..

[Feelings]

Hiya just wondering if someone knows what this is.
It came up the other night while I was in bed, at first it was just skin coloured bumps that were raised and itchy and then it stopped itching for most of the next day.
This morning it's sort of turned red but I've actually developed more on my other arm and around the back of my neck. It's really annoying me!

I've tried talcum powder, showering and keeping the areas clean.
DH has gone to get my hydrocortisone as it's rather itchy today.

I'm wondering if it's a heat rash?

[Feelings]

Anybody? It's actually spread further now. Burns and itches like mad... Warm baths makes it itch even more!

[BalloonSlayer]

I can't see it very well in the picture but my DC recently had a rash in tge heat which was not classic heat rash/prickly heat but (I think) heat related hives. Have a Google and see what you reckon. If it is, piriton may help.