痒疹 （ヨウシン） rash that accompanies a severe itch, prurigo

掻痒 （ソウヨウ） itching

麻姑掻痒 （マコソウヨウ） things happening exactly as one pleases (wishes), someone being very attentive to one's wishes

痒がる （かゆがる） to complain of itching, to be bothered by an itch (or rash, etc.), to feel itchy, to have an itch (or rash, etc.), to itch

痒い （かゆい） itchy

かゆいところに手が届く （かゆいところにてがとどく） to be extremely thorough, focusing on even the finest of details