洋蔥及蒜頭味

你可試用些放在手中, 加小量水卒云, 再用水過清. 或用發粉代鹽亦可.

you can use lemon or lemon juice to rub your hands...
crabtree & evelyn also has a "critus" handwash which can remove the odor of onion and garlic
btw, 吉之倒十蚊店出售一件專門用來去除洋蔥或蒜頭味的蛋型金屬 (i don't know the exact name of this product... sorry), you can use it to rub your hands when washing.