These bugs, known as sand fleas or jiggers, dig into your feet at the heel, sole, or toes. They cause a skin disease called tungiasis. You don’t feel it when they go in. But they grow up to 2,000 times bigger once inside your foot. This makes your skin itchy and irritated. Your foot may also swell and get ulcers. Some people get gangrene or tetanus. Chigoe fleas live in sandy, tropical places, and aren’t common in the United States.