I always use a hat, sun screen and most of the season use mosquito repellant.
Set up on a subject and then look at the ground–usually there will be poison ivy all around. The one time I forgot to tape my trousers to my hiking shoes (which I do to help keep ticks out), I got a bad case of poison ivy on my leg–several inches above the bottom of the trousers–I don’t know how it got me there. After I got a bad case of poison ivy on my wrist, I began wearing the top of tube socks on my wrist tucked into my long sleeve shirt and a pair of jeweler’s or film photographer’s white gloves. I was still getting slight amounts of poison ivy on my knees and other places on my lower and upper legs until I began wrapping the trouser legs in adhesive plastic. I may look strange, but I prefer not to get poison ivy.
Of course there are other risks. putting your hand somewhere and then after being stung noticing that there was a bee or wasp resting there. You don’t want to run or even walk fast if the trail is not really clear. There are always old fences with woven wire and/or barb wire and animal dens where you will step into the entrance. The last time I did that I had stepped back one foot from videoing the camouflaged caterpillar right onto such an opening. There was nothing to do but sit down right there unless I wanted to fall backwards.
Then there are the risks I have not yet thought of or encountered…