Hi! I don't want to worry you but I had a terrible experience allowing my hedgehog to play supervised on the grass last spring.
I made sure Albie didn't eat anything, but he somehow got a chronic case of some horrific parasite. The problem was, he was ill for about four months, and neither me nor the vet could identify the problem. He wouldn't eat, drink or get up at night - I had to force feed him with a syringe every morning - it was tragic to see an eight month old hedgehog looking so ill. Eventually, he passed a poo of pure blood and maggots. Luckily, he was easily sorted out with two weeks on antibiotics and de-worming/parasite medicine, but it really made him lose weight and be unhappy. Up until the faeces, I had no clue. :/
He made a recovery in late summer, so I bought him a very large kids' inflatable paddling pool and put it in the shade for him to play in. He absolutely loved it and I can't wait to use it again this summer. It's super easy to wipe clean, and keeps him away from any biological matter. Plus, it allows you to read a book or something - supervision is obviously needed, but you can take your eye off him if you're nearby as your hedgie won't be able to climb out
. I really wouldn't recommend even a playpen with a towel underneath - hedgehogs have such hyperactive noses they can easily sniff up maggots eggs! I know I sound absolutely mental but my silly little guy did manage to do it, so it's a legitimate concern
As for the flea treatment - it shouldn't be a problem as hedgies are quite sparse on the hair front, lol, but do keep an eye out. You might want to buy an insecticide rabbit shampoo (without tea-tree oil)
and wash his underbelly and feet after every outdoor session.
I wouldn't advocate regular flea treatments as hedgies are prone to dry skin. Nobody knows a lot about them veterinary-speaking, so who knows how they'll react to strong alcohol-based spot on worming. I know how pungent my cat's worming medicine smells - a hedgehog would be likely to self annoint too, and lick their back, as they seem to like medical smells, which could be disastrous! :0