Buzz Patch Instant Itch Relief Patches 27 countHow many do you need? One per mosquito bite. How long does this last when worn? Up to 7 days, and are completely waterproof. Is it safe? Yes, MagicPatch contain no chemicals and are safe. How does this work? The cross shape of the tape when stretched across the skin, adjust the skin to increase lymphatic flow, and help drain the mosquito saliva which is what causes the itch.