I've spent countless hours either on my hands and knees or bent over, messing up my back, looking for blood. One such instance I remember most was a hog hunt a few years ago in Mississippi. I had never shot a hog so when I poked a hole in this guy; I was determined to find him. Wearing snake leggings, I crawled on my hands and knees through the briars and the brambles and bushes where a rabbit wouldn't go. I found a spot of blood here and there but never the pig. And lucky for me, I didn't find a moccasin either.
I have spent hours on the blood trail of both elk and bear. If you don't hit them just right, they don't bleed a lot. So, what works best to follow a blood trail? I was told that if you wait till after dark and use a Coleman lantern, that the light will illuminate any blood on leaves or bushes. It took a couple of hours in the dark to dispel that rumor. Luckily, we did find the cow the next day but it wasn't by lantern light.
I've heard that certain lights when shined on the blood will make it look like a blue light on white. That didn't seem to work either.
Then I heard about an idea that has proven invaluable. When archery hunting (except for my hog hunt in Mississippi) I carry a small spray bottle filled with Hydrogen Peroxide. You can pick up Hydrogen Peroxide in any grocery or drug store and it comes in a little brown bottle. Cost is minimal so go ahead and waste lots of it. Find any small spray bottle and fill it. You want to use a spray bottle that you either squeeze the handle or push a plunger to spray the contents.
Maybe you remember your Mom putting Hydrogen Peroxide on a cut to help clean it. Do you remember how the blood frothed all white? It works the same on animal blood. With your little spray bottle, spray on any spot you think might be blood. If it's blood, it will instantly start foaming and turn bright white. Even if the blood has dried, it will react the same way. Lots of times when you're following blood in the fall, the leaves are orange, yellow and red and none of those colors help you much in finding blood. But if you spray the Hydrogen Peroxide on it, BINGO, you'll know if it's blood or just a dark spot on the leaf.
The little bottle doesn't weigh much and doesn't take up much space in your pack. Keep the big bottle in your camp or vehicle for refills. It's the best thing I've found so far for tracking wounded animals.