Small red sores on dog

Posting for a friend who’s isn’t on reddit:

Wondering if any one knows what these may be or how to treat them?

Ruby is 4 and never had any allergies but in the last few months had had these little red spots that then turn black and scab. Started on the tummy, then nearly cleared with some cream from the vet, then came back. Tried an antihistamines injection with the vet again but they are back and also more of them around the legs and upper leg.

They only thing I think is different is she's swimming twice weekly with her dog group, could be something in water, could be her rubbing in grass after, or drying and not getting rinsed straight away.

Any thoughts on how to help clear them? She doesn't seem to be bothered most of the time, but sometimes licks and scratches them till they go red.

Thank you in advance!