Problems tend to arise in the hot warmer weather or if she has been playing in the bush or dirty water. Wandering Jew (shown right) is particularly prevelant in Sydney and causes many nasty rashes. If it is in your garden get rid of it with a Glyphosate weed killer.
Longer haired dogs like retrievers and spaniels can get 'hot spots' from scratching itches with dirty claws and the wound becoming infected. Because they are difficult to see they can quickly become a very nasty sore that requires medical treatment.
For Millie we invested in an aloe vera plant (left) and if she starts to get a rash we treat it with the juice from the leaves. We find her usual rashes respond well to this treatment.
Consult your vet if the rash persists.
Disclaimer: The tips here are general advice only and if you are at all concerned about the problem please seek professional advice straight away.