You've been bitten by a mosquito - try not to scratch it.
Tips
usage
搔 specifically means to scratch (an itch) with the fingers. The compound 搔痒 means to scratch an itch, and 隔靴搔痒 (to scratch an itch through the boot) is an idiom for failing to address the real problem.
Three-stroke hand radical on the left - side form of 手, signalling that 搔 belongs to the manual-action family alongside 打 hit, 拉 pull, 推 push, 抓 grab. Scratching is a hand-led action, so the radical does straightforward semantic duty here.
Right side 蚤 supplies the sound - zǎo drifting to sāo, a regular z/s alternation. The flea imagery is a happy accident: fleabites are exactly the itch a scratching hand answers, so phonetic and meaning reinforce each other beautifully here.
