Most species of ladybug are not aggressive towards humans and therefore do not bite. All ladybugs have mouth parts that can be used for biting, but they are generally used for consuming small pest insects, such as the aphids which make up a majority of their diet. The one exception is the Asian ladybug, a swarming species that is more aggressive than the others.
Asian ladybugs pinch the skin with their mouths, but they are incapable of breaking the skin. However, some people are allergic to Asian ladybug bites and can get pinkeye from them. Because Asian ladybugs swarm, an encounter with them can result in multiple bites.