Threadworms spread when their eggs are swallowed. They lay eggs around your bottom (anus) or vagina, which can cause an itchy bottom. The eggs get stuck on your fingers when you scratch.
They can then pass on to anything you touch, including:
- clothes
- toys
- toothbrushes
- kitchen or bathroom surfaces
- bedding
- food
Eggs can pass to other people when they touch these surfaces and then touch their mouth. The eggs can survive up to 2 weeks. The larvae hatch from the eggs in your gut after you swallow them, and take 1 to 2 months to mature into threadworms.
Children can get threadworms again after they’ve been treated for them if they get the eggs in their mouth. This is why it’s important to encourage children to wash their hands regularly.