One of them will deal poison damage to monsters, while the other one will give you some extra healing if you need it. (twinfinite.net)
If something like viral gastroenteritis or food poisoning damages enough gut lining, lactase production and thus lactose digestion may be hampered for the duration of the sickness. (healthylivinghowto.com)
Gemstones can add poison damage to swords or improve the speed of heavy weapons, for example. (thesixthaxis.com)