u can try the liquid from bamboo charcoal (竹炭). this is a natural remedy for 濕疹.
You can find it from Franc x or Sa x. They're from Japan. i recommended it for some parents and they said it's effective. i have mild 濕疹 & it works well for me.
but i won't recommend babies below 1 yr old as i haven't test it myself
any brands will do. i'm using the one from 'vital charcoal'. only $42 from Sa xx. you may feel itchy after using that because it will dry out, but remember try not to touch it as your fingers may contain a lot of germs.