This is a somewhat embarrassing question, but after my painful experience in my last 100M, I am in dire need for some advice.

For most areas, like thighs or knees, I find Bodyglide more comfortable and effective. But I need something to prevent serious chafing in the unspeakable area at the lowest back, where your legs secretly meet.

What works best there, especially with heavy sweating, and running in dripping wet, sweaty shorts for hours. I have not tried anything there yet.

Do you wear compression shorts? That alleviates problems for me....but maybe when you run long miles even that does not help. Bag Balm might work good...but would have to be reapplied I think. Desitin has some water resistant qualities.

I used to use Bodyglide and other stuff, but I only use 2Toms Sportshield.

You can get it as a roll on or towlettes - which prefer.

I cut them in half and put the rest in a ziplock bag.

It can last for 24 hours and is great - no more chafing - ever.

I also highly recommend 2Toms Blistershield powder for your feet.

Thanks for the lots of suggestions and comments!

I use Aquaphor or Vaseline on my face in winter to prevent frostbite. For the current anticipated use, Vaseline might be better because it is softer, and not so sticky.

Good to know there's a scent-free Desitin, too. When my kids were infants and toddlers, I loved that smell, but for running, it seems a bit spicy, not exactly as discreet as I'd like it to be. 

Charles, I'll look into the 2Toms. The towelettes would be great to take along and apply as needed.

I have had great success with Vaseline, but as Mandy mentioned, you need to get the name brand stuff. The off brand just doesn't get it. Bodyglide, band aids, and compression shorts takes care of everything else for me, though.

Getting your crew to apply it is a bit tricky though.

Compression shorts seems to be the magical gadget.

Now I am not sure, maybe I've used the wrong type of compression short (actually, capris) on the last 30 miles of my 100M, but I always thought that these were the cause why I got chafed so badly.

I was wearing my usual running shorts all day (3" inseam), and I did not get chafed, or maybe just a tiny little bit on the inside of my upper thighs. So to prevent more chafing, I changed into the capris, and shortly after that, severe chafing started (in this unspeakable area). I always thought that the capris were just too tight, compressing the cheeks, and that's why I got chafed.

I was convinced that with the shorts I would not have gotten chafed because there was air flowing freely, and wiggle room.

Am I wrong on that?

Or are the capris just too tight?

I have bought shorts with longer (5") inseam to prevent chafing on the thighs, but they don't seem to fit the bill 100%, either. The material is a bit scratchy, more than my Saucony shorts, which are really very soft and smooth. I have worn the new shorts on runs up to 20 miles, but I'm not convinced if they will chafe the thighs after 60+ miles, or not.

I'm unsure if I should buy compression shorts (recommendations?), really soft and gentle ones, use my usual Saucony shorts, or use the new shorts.

I don't have time any more to try out any shorts on 20+ mile runs.