Crabs are teeny tiny little animals that live in the hair follicles. They might look like like brown spots on your skin. You can't really see their body until it is outside your body.
Crabs make you itch like crazy. They can cause a rash. If you have an allergy they can cause other symptoms.
If you have them the best products are by prescription from a doctor. But there are over the counter medications you can get at a drug store.