Cleaning Dirty Feet

Let him walk around barefoot outside more. My kids never had dirty feet like that because the cement was constantly exfoliating them.

Soak his feet in warm water for a while -- let him watch tv or something-- and then, use olive oil and a washcloth. You don't need goo gone-- olive oil will get tree pitch (sap) off skin easily, it works.

And then, leave the kid's feet alone. The skin will gradually slough off and replace itself. I wouldn't encourage scrubbing too much, just because you don't want to discourage him from going barefoot. Dirty feet aren't a big deal. :) In my opinion, dirty kids are often very happy kids!

I suggest that his feet are not dirty. They may be stained by something in the water or on the pad.

I stayed with my grandmother every summer. She washed my feet in a basin everynight. Once the dirt was gone, she wasn't concerned about any color left. She washed them so I wouldn't dirty the sheets. My parents were even less concerned. They gave us a wet wash cloth to wipe off the dirt. They didn't even look at them to see if we got it all.

I remember always having dirty feet in the summer. It was no big deal.

let him soak in a bath....

are you sure he's not tanned?? A few years back, my youngest son looked dirty on his back after a day at the pool and splash park - turns out?? he tanned....

I would try a really long bath and gently rub with some baking soda.

Updated

Oh, use lava soap (pumice)! Search it and it is available to purchase online or in stores. It gets a lot of things off. The other option is a good long day at the beach or lake. The sand is an exfoliant that will likely rub anything foreign off (in addition to gently sloughing off old skin). These options are all without chemicals, always a plus in my life!

I would try soaking his feet in a tub or plastic bin. A good long soak, in plain warm water, often gets through where scrubbing won't.

By the way, I love sugar and coconut oil! I make my own scrub for the shower from it, using coarse sugar, like turbinado. My grandmother was from Sweden and she taught me about oil and sugar scrubs a long, long, time ago. She said it was very common in Sweden and she learned it from her mother. (She didn't use coconut oil, just mineral oil and regular sugar.)

Soak in water with some added plain white vinegar.

I have a very gentle foot scrub brush - almost like a nail brush. Natural soft bristles (not plastic ones). It does tickle their feet but if you used that with a scrub, it might work better than the washcloth.

Scrub with a brush that you'd use on your finger nails after soaking in a bubble bath.
If he has tar stains on his feet you might have to use nail polish remover or Goo Gone to get it off because soap alone won't work on that.

Additional:
When our son was young he wore Crocks all summer.
The holes in the shoes meant he tanned in some places more than others.
For awhile he had this set of 'leopard' spots (tanned places) on his feet that he thought were so cool looking!
My husband and son both tan a lot darker than I do.
I go from white to red to peeling and barely tan at all.
I wear a big baggy tee shirt and hat with a big brim to cover up most of the time.
They get pretty dark from very little sun exposure.

Are you sure it's regular dirt? If so, it's really embedded somehow, and the only way to get rid of it is exfoliation. You need more of a scrub than sugar, which dissolves in water. Maybe a paste of baking soda and a tiny bit of water, and a brush? I also know that baking soda and white vinegar, when combined, really react - think science project volcanic "lava" or homemade non-toxic drain cleaner - so maybe outdoors in a deep wash bin or bucket, with plenty of overflow room, plus a hose to wash it away after it overflows? Or have him sit on a stool in the bathtub with his feet in a plastic bin so the initial solution doesn't just run down the drain.

I'm also thinking there was some sort of coating on the pad, perhaps something that has actually stained his feet. I know that there's often tar that washes ashore on beaches, and you need a good degreaser for that (maybe Dawn dish liquid). Someone below suggested Goo Gone, which makes sense if he's sticky and if you do it outdoors in a well ventilated area, then have a way to rinse it off.

Letting it wear off is also an option. If you've scrubbed and nothing is coming off, then it's not going to come off on your floors or rugs either.

When my kids are super dirty like that, they soak in a bubble bath for a good 30 minutes.

A nice long soak while playing with toys in the bathtub.

I agree with the soaking...if he was at a splash pad maybe it's dye from whatever they put on the ground at those things. It may just be something you'll have to accept for a few days until it wears off. But they shouldn't be "dirty" after what you described. Welcome to summer! :)