Third on the antiperspirant. Only takes a second and doesn’t increase the laundry load.
This is my perfect solution: a “split slip” and a longer version. I love these things!!
Last year, I started a teaching job at an Orthodox Jewish school. So, no pants for me, just long skirts.
I wear anything from a size 18 to a 24 on my bottom half, and I gave up on skirts a long time ago. I had to completely revamp my wardrobe.
The first week or two was the hardest. It was hot in the building, I sweat a lot. I tried to wear pantyhose - big mistake. I had a combination chafe/prickly heat rash and was miserable.
After another few weeks, I got the hang of it.
First, if you can stand it, stop shaving the insides of your thighs. The hair there acts a bit like ball bearings. Second, don’t be shy about the Glide or other silicon based skin lube. The Monistat brand worked for me. Powder didn’t help after the first thirty minutes.
Pantyhose is the devil, because it traps moisture, which makes chafing worse. I took to wearing knee highs, because my skirts were long enough. I also took whatever opportunity I could get to sit at my desk and air things out.
I got to the point where I was happier going without pettipants or the equivalent. My body learned to sweat enough to lubricate, but not so much to irritate. So, if you’re going to wear skirts, you’re best off doing it consistently for several weeks.
Even at a size 10 my thighs chafe. These call themselves “thermal” but I’ve worn them in very hot climates when I had to wear a skirt.
ETA: phouka, been there and done that. My answer then was silk boxers, because it entertained me to know that I was wearing “men’s clothing” under my skirts-below-the-knee getup.
I always wear shorts underneath my skirt or dress unless I’m wearing hose.
I used to get worse chafing than I do now because I have lost weight. I think once I’m thinner this won’t be an issue, but you never know.
Resurrected! I’ve been away from the Dope a few days but I had to respond - I am truly impressed with the variety of solutions presented here, and glad that you’ve all managed to find good options. But, alas, few work for my particular mileage. To wit:
Pettypants, ruffled: Too bulky. I just can’t imagine these under a slim skirt, and even in the most voluminous peasant skirt I don’t want to feel (or look) like I’m wearing a diaper.
Pettypants, nylon: We’re talking about 100 degrees with humidity here. Anything other than natural fibers is an unacceptable sweat-factory.
Split skirt: Anything that just hangs from the waist and doesn’t cling to the legs is a problem in two ways. First, the waist-to-crotch seam is usually too long and my thighs rub together anyway. Second, the legs ride up and I end up with chafing AND a bunch of fabric crunched up between my legs. Sexy.
Pantyhose/tights: Pantyhose = never in my wardrobe. Sure, tights work great in the fall and winter. But I’m talking about on a hot summer day, throwing on a skirt and t-shirt and flip-flops to run errands sort of thing. Adding more layers and bulk are anathema to this.
Granny panties/thermals: Actually this is the closest I’ve seen yet to being the Holy Grail. But why must designers presume that if I want thigh coverage that I must also want them to go up to my chin? My skirts usually sit slightly below the belly button. Is it so absurd to want my undergarments to sit there too? If not for that, these would be perfect.
Antiperspirants/Glide: I don’t use antiperspirant, but your testimonials are encouraging. This is the one I might actually try next summer. I’m still a little worried that any topical goo wouldn’t work for a full day, but your posts don’t lie. Picking up a roll-on is cheaper and easier than mail-ordering underwear that may or may not fit, anyway.
Still, what burns me is that I can walk into Target today and find a three-pack of practically any style cotton panty on the market - bikini, string bikini, high-waist, low-waist, thong, hipster, “boy short”, stripes, solids, prints, etc. It is so completely outlandish that ONE manufacturer simply make a bikini panty with longer legs? Surely one of you creative/crafty Dopers can fill this much-needed niche? OK, so maybe my purchases won’t keep a whole business afloat, but I’ll be happy to test-drive your prototypes! 
Thanks for bumping this, Rachel. I mean to respond to this post and forgot. So, Phouka, in the last paragraph you imply that now you can wear skirts without any type of aid. Is this true, or do you still need the glide/monistat?
You can get these thighshapers from Barely There. Their stuff is very lightweight, and this one, as shown in the picture looks to be a touch below the belly button. You could probably fold it down a touch with no bulking.
I don’t have this problem, but I wonder: would a couple of large square bandages work?
Humm - I must have very tough inner thigh skin (although no one has actually mentioned it).
I wear skirts all the time, my thighs touch somewhat (particularly in a pencil skirt), I stomp all over the place and have never noticed this.
FWIW, my skin is quite dry and I live in a very arid climite so perhaps the lack of skin oil/sweat is the key?
If that’s the case I would suggest a cornstarch based dusting powder - they’re great for absorbing extra moisture.
I’ve just been wearing men’s boxer briefs. Yeah, there’s a little extra room in the front that I obviously don’t need, but they’re really comfortable, they come in various fabrics (I like the cotton ones, but some of the others are good too.), and they are light enough to go under a summery dress/skirt without a problem.
:Goes and steals some of Mr. Lissar’s boxer briefs:
That’s a really good idea. I have a lightweight stretchy slip I’ve split into a pair of shorts, but boxer briefs would work under loose skirts.
Not bad, not bad. That can’t be natural fibers though right? I am suspicious of “shapewear” because of the implication that they, well, “shape” and therefore constrict. My only experience has been with Spanx, which make me feel like I’m trying on Barbie pants. If I’m going for the ease of a skirt, I don’t want to put on anything that requires more effort than a pair of undies.
Slight hijack - why do they always have such skinny models in the product photos of stuff like this? These are exactly the people who don’t need, want or use such items, and it just makes the product look extra-ridiculous.
Hey, sorry it took me so long to respond.
Yep. After about a month of wearing skirts every friggin’ day in a hot house without ventilation, running from classroom to classroom, manhandling furniture and art supplies, I got to wear I just wore cotton panties and the skirt du jour.
I did focus on cotton skirts. I’m not big on artificial fibers. They don’t feel right to me. I also lost my ladylike posture when I sat at my desk. Instead, I sat with my knees as far apart as they could go under the desk, and my skirt hiked above my knees. If I could have installed a fan down there, I would have. However, I did survive. My body adjusted its mad sweat levels, and the weather cooled down.
I’ve been looking for pettipants but I never knew what to call them. So, thanks everyone for the links.
In the meantime, I’ve become a fan of shapewear. However, I usually buy a size or two too big, since what I really want is to prevent chafing and shaping is secondary. That’s been great for work, but it’s still too constricting to be comfortable for really casual wear. I hope the pettipants will solve that problem.
I am a designer specializing in pear shaped women’s wear and I have been thinking of a solution to this problem for years.
I’m working on a pattern now.
I too live in HOT weather. I sweat like crazy, and though not nearly as bad as 50 pounds ago, I do chafe.
Slips ride up, Spanx come too high, are uncomfortable and make bulges at the top and bottom. I’d like to have something that is supper thin around the low waist and thicker in the chafing area, but either thin or non existent on the outer thigh.
That is my mission!
This is a bit of an old thread, but there has also been some discussion about chub rub inmy recent thread about holiday clothes here, so you’re welcome to join in. 
I know this is a zombie, but Forever 21 has cotton “tights” that go only to mid-thigh. I wear them under my dresses and skirts to prevent anyone from getting flashed. They are breathable even in hot weather.
I (a guy) have always had this problem when I sweat while running or hiking. I’ve found that for moderate exercise, the men’s/unisex equivalent of loose fitting half-thigh long pettipants works very well, but for many hours of hiking while perspiring, snug fitting half-thigh long underpants work better, for there is less friction from fabric movement. Although silk feels nicer when dry, poly works better when perspiring, for it holds less water. For truly sodden long hikes, I apply some zinc oxide (e.g. Penaten cream) before I set off, which works wonders, but is a bit messy.
Body glide or any other runner’s lube - I’ve used it through half marathon and long weighted marches with no issues.