隔靴掻痒[kakkasouyou] being frustrated because something is not quite as hoped (just as one cannot scratch an itch from outside a shoe)
歯痒い[hagayui] impatient
瘙痒[souyou] itch
痛痒[tsuuyou] pain and itching
痒い[kayui] itchy

痛し痒し[itashikayushi] delicate or ticklish situation
痒み[kayumi] itch
麻姑掻痒[makosouyou] things happening exactly as one pleases (wishes)
痒がる[kayugaru] to complain of itching
むず痒い[muzugayui] itchy

痛癢[tsuuyou] pain and itching
伎癢[giyou] itching to show off one's abilities

癢疹[youshin] rash that accompanies a severe itch

乾癬[kansen] psoriasis
苔癬[taisen] lichen
疥癬[kaisen] scabies
頑癬[tamushi] ringworm (of the body)
皮癬[hizen] scabies

皮癬ダニ[hizendani] itch mite (Sarcoptes scabiei)
疥癬虫[kaisenchuu] itch mite (Sarcoptes scabiei)
頑癬[gansen] ringworm (of the groin)
白癬[shirakumo] scalp ringworm
扁平苔癬[henpeitaisen] lichen planus