If you're developing pimples, I find a wipe of surgical spirit stops them from getting any worse. I also use talc if I know I'm going for a long ride on a warm day.
alternatively, buy a colour of jodhpur where any sweaty marks won't show up! (dark dark black seems to work well, grey, cream, purple and whites to be avoided!) Have you tried the lightweight breeches, or even riding in thinner socks (as I seem to overheat the most if my feet are very warm!)
another thing may be to look at your saddle, it may be making you sweat more/be a bit slippery which won't help!
I find cotton undies are by far the worst thing to wear as far as this problem is concerned as they hold moisture and don't wick it away.
Dunno what jods you're wearing but the ones with clarino full-seat IME are a total nightmare as they tend to hold in moisture so it feels really nasty and clammy in there. Yuck. You only have to ride in the rain in these type of seats to realise just how much moisture they're capable of soaking up: horrid! Cotton jods may seen a cool choice but they will hold in the moisture and won't diffuse it.
Know it sounds daft, but ditch the cotton and try switching to synthetic: Primark do some lovely little no-seam full briefs which are superb for riding, and cheap and cheerful with it. Then ditch your cotton joddies and treat yourself to a pair of Kerrits, they do special ones for summer riding. Or try some of the endurance websites (Performance Equestrian for e.g.) as endurance riders know what's what, and how to keep cool, and there are some really nice riding tights in special wick-away technical material which you can buy. Well worth it IME.
I'd betcha a tenner that this will improve your situation enormously OP.
Have you recently changed your saddle? I had a friend that spent a fortune on a Wow saddle and although she loved it, her bottom was always soaked with sweat after riding in it. Didn't happen with her old saddle.
Interesting comments, thanks folks. I have got a new saddle. Wonder if it's that? I do use synthetic jodhs sometimes. I have Heather Moffatt seat saver would that just soak up the sweat? Yuk!!
Try riding tights that endurance riders use rather than jods. BTW we swear by natural fibres in contact areas for humans & horses (such as wool or cotton numnahs)! Also take a change of clothes to yard so you can change after riding. Consider a wool seat saver.
I've got a HM seat saver OP - I bought it secondhand on e-bay for a saddle I'd bought, an older one which was a good make which fits my trad perfectly and which I was lucky to have got for £50 at a car boot, which was a nice saddle but a bit hard, so I thought to use the HM seat saver on it.
It actually was like sitting on sandpaper The bleddi thing rubbed me in all the awkward bits (blushes delicately), and after about half an hour into a hack I was acutely aware of the growing discomfort in a certain region......... and nothing else. I tried it a few times more, just to try different combinations of underwear and jods, but it doesn't change the intrinsic fact that the damn thing isn't helpful! I have ridden on a suede saddle before, my last saddle was a suede seat, and I found it fine, though I did find that if you DO sweat, then a suede-seat saddle is bad news as you get a rather embarrassing damp mark on the seat if you ride and sweat in it. VERY embarrassing, and a reason why I wouldn't choose a suede seat again (plus the fact that over time, a suede suede inevitably stretches and bags up and looks awful plus is uncomfy). Having said that, I ride in a treeless saddle which had a suede seat on it originally, but over time the suede has become a bit more polished and smooth, and I'm fine with that one, its a lovely saddle to ride in.
I've kept it, as I have a friend who rides my traddie in that particular saddle, and she likes the blessed thing! But it was torture for me, I can tell you!
Don't know if it would help with your problem OP, mebbe worth a try (they come up regularly on e-bay, ha ha I wonder why), but my feeling would be that it just make your situation a whole lot worse.
I've just had a thought (edited): during my search for the "perfect" saddle, I did come across some which were made so that there is a gap between the two panels. Sorry, probably that doesn't make much sense, but they're made that way so that each side of the saddle can move independently rather than having the centre gullet down the middle which is rigid and doesn't move. Sorry, can't remember the name of the saddle(s) I looked at, think if you fed in "endurance saddles" into a search engine you might come up with it? Think they were made abroad, and were expensive...... but it just might be what you're looking for as if there was no central gullet, or a partial one, then you would have cool air circulating in your "vital parts" and would be able to ride so much cooler?? I must say, I liked the look of the saddles, but my budget sadly won't allow at present.
Anyone else know the saddles I mean? Anyone got one?
Glad I am not alone at least! My endurance jodhs are worst of all I think! Not tried the Heather Moffatt seat saver in this country, I use it abroad on a trekking holiday. I think the new saddle could be a contributory factor. I have a fluffy seat cover I could try but sure it will make me warmer so counter-proactive! Off to google technical fabric knickers!