A white solid, it occurs as an impurity in xylenols and as such is used in the production of some commercial phenolic resins.
At concentrations greater than 140 μg/L (typical sensory threshold) it gives the wine aromas described as barnyard, medicinal, band-aids, and mousy.
The level of 4-EP is roughly proportional to Brettanomyces concentration and activity, and can therefore be used as an indicator of the yeast's presence.
There are significant differences between strains of Brettanomyces in their ability to produce 4-EP.
Coumaric acid is sometimes added to microbiological media, enabling the positive identification of Brettanomyces by smell.