Boyfriends rash?

It started a week or so ago with one red sport on his neck/collar bone about the size of a fingernail. But yesterday he has little red bumps all over his chest and arms.

At first I wasn't so worried but of course I googled it and now Im worried if its contagious! Or dangerous.

He has been mildy unwell recently too. Only cold symptoms like a blocked nose.

Any ideas what it could be?