The plant Artemesia absinthium (or “wormwood”) is mentioned several times throughout the Bible. Solomon writes that the adulteress is as “bitter as wormwood” (Prov. 5:4). Likewise, Moses compares idolatry and serving other gods as “a root bearing poisonous fruit and wormwood” (Deut. 29:18; c.f. Jer. 9:15; 23:15; Lam. 3:15, 19). Osborne explains that the taste of wormwood “is so potent that one ounce of it can still be detected in 524 gallons of water!” Wormwood itself is not poisonous, but it probably is symbolic of the fact that the people have made a horrible, bitter decision to fall under the judgment of God.
 Osborne, Grant. Revelation. Baker Exegetical Commentary on the New Testament. Grand Rapids, MI: Baker Academic. 2002. 354.