From my own experience, you wouldn't need to get near a pinhole leak in a pressurised hydraulic line with your hand before you discovered where it was coming from. There would be a choking/blinding mist in the immediate vicinity, that, unless you were wearing the appropriete clothing/equipment, would for sure, stop you from getting anywhere near it until the pressure was dissipated.
Hydraulic fluid, typically manufactured by Monsato and called Skydrol and is a purple coloured synthetic phosphate/esther(sp.) based fluid(used on large transport type A/C). Is particularly unforgiving when it enters you eyes. It is extremely painful and has a burning sensation that can last for what seems like an age. It can be neutralised with a saline eye-wash bottle or if that is not available then milk will also work.
Basically, you have to be extremely safety-conscious when you are working with this fluid, even just getting it on your hands can bite you in the harris if you are not careful, a small rub of the eye will give you at least 10 minutes of pain! Eye protection is a must, and gloves are also recommended.....Although it will destroy/distort most latex/rubber types within a short while which really hinders your work.
Just my 2 cents worth.....