When I first became pregnant, finding a mild soap for my new baby was important to me... although, I really wasn't aware of all my options - and was still a little mainstream on my choices. However, today, I am happy to find not only a safe-for-sensitive skin (and the rest of the family) soap, but a natural resource, and one right in my back yard. The buckeye. How neat, right? Buckeyes, and MANY plants, are high in saponin, a naturally occurring "soap." Saponin is also a toxin if it enters the bloodstream, but for washing it is fine. It is more harmful for cold-blooded animals, and historically used for fishing to stun the fish (better in water that isn't flowing too fast because once fresh water overtakes the poisoned water, the fish are revived.... though, you would want some flowing water so you don't kill all the fish at once). Many foods we eat have saponin, but not in high enough quantities to harm humans when consumed at a natural level and as such have health benefits, though you just want to be aware of what you may be ingesting. But, this is about the washing, not the eating...
Be truly eco-friendly by using a renewable resource, avoiding the manufacturing/polluting process, and not even driving to get them. Get out in nature, take a hike with your family, and enjoy nature's resources.
All I did for this was break open some dried buckeyes, place them in warm water, and agitate - very vigorously. I used them (4) to wash a wool diaper cover. These are reusable according to what you're washing, the temp. of your water...etc. The higher the temp. and the more agitation, the more saponin is released. You can use this for a cold wash, or place the shells in a bag and just drop them in the wash for a warm/hot wash. They won't suds like store-bought detergents, but the suds aren't the cleaning powers - its the saponin (even in store-bought products) and the agitation that creates cleaning power. Once finished, just let them dry and reuse - as long as they're sudsing, they're still releasing saponin and can be reused. You would use more nuts for a load of laundry to release more saponin. They may leave a buckeye scent behind (which is naturally pleasant, but not your typical fresh scent), so adding a few drops of essential oils to the wash will create any smell you like. And, oh, the softening powers - just wash your hands with them and see what I mean! Nuts (of many kinds) can be stored in water-tight containers below frost level or in a root cellar over the winter and, actually, for quite a few years with the right conditions and contain varying levels of saponin - so go out this fall and gather up some eco-friendly washing nuts and store for the rest of the year.