After about three days, the redbug is full. The itching caused by redbugs is an allergic reaction to the redbug's saliva. You should try not to scratch it, because it can get infected. To keep redbugs from biting you, you can tuck your pant legs into your socks and use insect repellent, especially on your ankles. You should also stick to nature trails and stay away from areas with lots of moss and shrubs on the ground.
Redbugs avoid bright sunlight, so hiking in sunny areas is a good idea too.
As soon as you get home, take a hot shower and lather up with soap a few times. This will remove any redbugs that have not bitten in yet. You can use some kind of anti-itch medicine to help. Like redbugs, they wait on small bushes, moss, and sticks for an animal to walk by. They jump onto you and bite with their sharp mouthparts.