lumps in the sun

I have a blue staff he is 8 months old. When its a hot day and he is in the garden he gets a couple of lumps on him. His hair stands on end on the lumps they can be quite big and are in different places all the time. Once he's been indoors out of the sun for a while they disapear. Does anyone else have this problem or know what it is? Is it just that he is getting too hot? Thanks

Unfortunately it's not something Ive come across before, it sounds like its something to do with the sun. I'm sure some will pop along soon who can help.

Why not come and say hi.
https://staffy-bull-terrier.niceboard.com/f7-new-member-introductions

Never heard of it either, could it be something to do with him sweating...

Vinny gets this, I can't remember what they're called but it's exactly as you describe and they disappear once he cools down. Guess it's like a heat/allergy rash. Doesn't seem to bug him though.

Sounds like whatone of our dogs gets in the spring summer, I think it is related to an allergen though. Perhaps he was bitten by a bug or touched a plant which he is allergic to?