Severus' head was bent over the cauldron in his lap. He was almost nodding off, drowsy with the slow, familiar swirl of warmed oil smoothing over metal.
Al's voice pulled him out of the idle, tired trance. He blinked. Frowned. "Of course I don't have metallic allergies, I'm a Potions Master," he replied with some asperity, before adding absently, "No doubt an aversion to silver was one more handicap for Lupin in Potions."
"As for aversions to wearing jewellery, there are places for charmed amulets and talismans, but I dislike relying on any external props, things that can be taken away. It's why I've taken such pains, over the years, to perfect my wandless casting."