Styrax is a genus of about 130 species of large shrubs or small trees in the family Styracaceae, mostly native to warm temperate to tropical regions of the Northern Hemisphere, with the majority in eastern and southeastern Asia, but also crossing the equator in South America. Common names include styrax, or the more ambiguous storax, snowbell, and benzoin.
The genus Pamphilia, sometimes regarded as distinct, is now included within Styrax based on analysis of morphological and DNA sequence data. The spicebush (Lindera benzoin) is a different plant, in the family Lauraceae.
Styrax trees grow to 2-14 m tall, and have alternate, deciduous or evergreen simple ovate leaves 1-18 cm long and 2-10 cm broad. The flowers are pendulous, with a white 5-10-lobed corolla, produced 3-30 together on open or dense panicles 5-25 cm long. The fruit is an oblong dry drupe, smooth and lacking ribs or narrow wings, unlike the fruit of the related snowdrop trees (Halesia) and epaulette trees (Pterostyrax).
The chemical benzoin (2-Hydroxy-2-phenylacetophenone), despite the apparent similarity of the name, is not contained in benzoin resin in measurable quantities. However, benzoin resin does contain small amounts of the hydrocarbon styrene, named however for Levant styrax (from Liquidambar orientalis), from which it was first isolated, and not for the genus Styrax itself; styrene is used to produce polystyrene plastics, including StyrofoamTM.
There is some degree of uncertainty as to exactly what resin old sources refer to. Turkish sweetgum (Liquidambar orientalis) is a quite unrelated tree in the family Altingiaceae that produces a similar resin traded in modern times as storax or as "Levant styrax," like the resins of other sweetgums, and a number of confusing variations thereupon. Turkish sweetgum is a relict species that occurs only in a small area in SW Turkey (and not in the Levant at all); presumably, quite some of the "styrax resin" of the Ancient Greek and the Ancient Roman sources was from this sweetgum, rather than a Styrax, although at least during the former era genuine Styrax resin, probably from S. officinalis, was imported in quantity from the Near East by Phoenician merchants, and Herodotus of Halicarnassus in the 5th century BC indicates that different kinds of "storax" were traded.
The nataf (נטף) of the incense sacred to Yahweh, mentioned in the Book of Exodus, is variously translated to the Greek term staktḗ (στακτή, AMP: ), or an unspecific "gum resin" or similar term (NIV: ). Nataf may have meant the resin of Styrax officinalis or of some other plant, perhaps Turkish sweetgum, which is unlikely to have been imported in quantity into the Near East.
Since the Middle Ages, Southeast Asian benzoin resins became increasingly available; today there is little international trade in S. officinalis resin and little production of Turkish sweetgum resin due to that species' decline in numbers.
"[The Arabians] gather frankincense by burning that storax which Phoenicians carry to Hellas; they burn this and so get the frankincense; for the spice-bearing trees are guarded by small winged snakes of varied color, many around each tree; these are the snakes that attack Egypt. Nothing except the smoke of storax will drive them away from the trees.
Tincture of benzoin is benzoin resin dissolved in alcohol. This and its numerous derived versions like lait virginal and Friar's Balsam were highly esteemed in 19th-century European cosmetics and other household purposes; they apparently had antibacterial properties. Today tincture of benzoin is most often used in first aid for small injuries, as it acts as a disinfectant and local anesthetic and seems to promote healing. It can also be added to boiling water to produce fumes which when inhaled have a soothing effect on the lungs and bronchia, helping recovery from the common cold, bronchitis, or asthma. Benzoin resin and its derivatives are also used as an additives in cigarettes due to this soothing effect.
The antibiotic activity of benzoin resin seems mostly due to its abundant benzoic acid and benzoic acid esters, which were named after the resin; other less well known secondary compounds such as lignans like pinoresinol are likely significant too.
Some styrax species have declined in numbers due to unsustainable logging and habitat degradation. While most of these are classified as Vulnerable by the IUCN, only four trees of the nearly extinct palo de jazmin (S. portoricensis) are known to survive at a single location. Although legally protected, this species could be wiped out by a single hurricane.