Don't scratch - the more you scratch, the itchier it gets.
Tips
memory
The radical 疒 (illness) hints that itchiness is a bodily discomfort. The right side 羊 (yáng, sheep) gives the sound - imagine a sheep that can't stop scratching itself.
Sickness radical wrapping the upper-left - pictures a person lying on a sickbed (the bed-form of 爿 plus a 亠 lid). It marks 痒 as a bodily ailment, even a minor one like an itch. Same radical heads the entire illness family: 病 (sick), 疼 (ache), 痛 (pain), 疯 (mad).
羊 (yáng) tucked inside the sickbed - supplies the sound, lightly retoned to yǎng. This is the simplified form of 癢 (which had 養 as phonetic). The same yáng/yǎng family runs through 洋, 样, 养, 氧. Here it is purely sonic - meaning is all in 疒.
