Thigh irritation is common and usually happens from friction against trapped moisture in the upper layers of skin, and where there isn’t really adequate airflow in that area to allow the skin to “breathe”. Since the diaper is between this area that you may naturally have a little excess moisture then it makes sense to have some chaffing. Diapers (
any type) just aren’t breathable—they are designed to not allow moisture to pass through.
A lot of “the best” solutions end up requiring a person to add a thin additional layer of breathable clothing, such as leggings, under what they’re already wearing. This thin layer helps to wick just enough moisture away from the skin to be used as a barrier to the rubbing. You may just want to wear shorts (
“bike shorts” are helpful since they aren’t lose and flowy) or leggings over your diaper and underneath your typical clothing, or consider trying those onesies with the longer, shorts style legs such as the
rompers from Tykables.
A lot of people with larger thighs will powder their skin with baby powder, women’s powder, or anti-chafing specific powder throughout the day to reduce chafing and skin irritation. There are also “chub rub” creams that some find success in using. I’m not sure these options would help with diaper chaffing on the thighs (
because it isn’t typical skin-on-skin chaffing but, instead, skin-on-nonbreathable-fabric) but they are low cost enough to consider trying out if something sounded really cool to you. A quick Google search for anything I’ve mentioned above should find you a few things to potentially try.
As a last thought, it could be possible that the diaper leg gussets are not actually tight enough on your body. If there is even a small gap the it would allow surrounding skin to collect more moisture (
even if you don’t wet the diaper since that area of the body is naturally prone to sweating and being more moist than other areas), and allow the diaper more movement to cause more friction. Diapers, including around the legs on the crotch area, should rest against your skin. Saying from experience, cloth diapers can end up with a gap with the more layers inserted. You could try to find cloth diapers with double gussets or give a disposable diaper a try to see if the fit is better. Pocket diapers can be finicky anyway.