While they may bleed for a while, and possibly itch, leech bites are more annoying than dangerous. They’re essentially harmless, making them preferable to mosquitoes, ticks, and most other bitey creepy crawlies.Some leeches carry viruses, bacteria, and parasites, but don’t stress, it’s very rare for these to be transmitted to humans.However, it’s worth noting that a small percentage of people have an allergic reaction to leech bites.