
Have a look for mentholated talc (talc with menthol crystals in it) it's what they use in tropical countries for prickly heat with or without the rash and it does work. Don't get it near your bits though! lol
If you do have the rash, then Tiger Balm works really well to stop the itching, same with hives or chilblains. If you go to an ethnic food shop you might be able to get something similar to Tiger Balm that has methyl salicylate in it (an aspirin derivative) which really does take the itch away but obviously not for use on people who have issues with aspirin.
If you can find it the Mentholated Talc then it is incredibly refreshing in hot weather, especially on hot tired feet. Wonderful getting a foot massage with that stuff.