This story was updated with new reporting and data on October 23, 2019.
If you’ve spent any significant amount of time in the world of cannabis, you’ve probably encountered the term “terpenes.” They’ve been touted as the next big trend in cannabis skin care, and celebrated for their (still largely unproven) therapeutic potential. People are now even cooking with terpenes — and yet most of us still have only the fuzziest understanding of what terpenes are or why we should care about them.
With that in mind, cannabisMD has put together a one-stop guide that answers all your most important questions about cannabis terpenes in plain English.
So now, without further ado, let’s dive in.
Terpenes are organic compounds that can be found in cannabis and many other plants (more on that in a second). There are around 20,000 terpenes in total, though only a fraction of these are present in the cannabis plant — most estimates suggest it has around 100 terpenes, though some experts believe that it could contain 200 or more.
In both cannabis and other plants, terpenes serve a wide range of roles, but their biggest impact can be detected in the plant’s taste and scent. For this reason, terpenes are often the primary component in various essential oils derived from these plants. So if you’re a fan of aromatherapy, you’re already intimately familiar with terpenes, even if you don’t know them by name,
Speaking of names, many people also wonder, “Are terpenes the same thing as terpenoids?” From a scientific standpoint, this usage is technically incorrect, as terpenoids contain certain components that terpenes themselves do not.
However, in the lexically flexible field of cannabis — where products made from plain old hemp seeds are often passed off as hipper, more exotic “CBD” or “cannabis sativa” items — the terms terpene and terpenoid have come to be used interchangeably by many. If you do the same, you won’t win any awards for scientific accuracy, but you’ll also be unlikely to be misunderstood. And while mixing up CBD oil and hemp seed oil might leave you stuck with an overpriced, less-effective item in some cases, there are few potential downsides from walking into your local dispensary and requesting a terpenoid-rich cannabis product (other than possibly getting a weird look or two).
While cannabis connoisseurs appreciate terpenes for the unique flavors and aromas they impart to specific strains, they serve a more practical purpose for the cannabis plant itself.
Secreted in the resin produced by the plant’s trichomes — tiny, hair-like structures found primarily on its flowers and leaves — terpenes serve as a valuable defense mechanism against hungry insects and other potential threats. They do this in two ways: First, by making the plant unappetizing to such pests, and second, by attracting predators that can feed on these would-be marauders, thus allowing the plant to reach full maturity unscathed.
As a result, it’s unsurprising that a cannabis plant tends to produce the most terpenes near the end of its growing cycle, when its ripened buds and leaves present the most attractive target for ravenous diners. The types of terpenes created by a given cannabis plant depends in large part on specific environmental factors, such as the most common predators in its area, which has led some cannabis growing experts to suggest that the substandard flavors and aromas of many medical cannabis strains are a result of the sterile conditions in which they’re grown. According to this theory, since these plants aren’t forced to defend themselves from external threats, they end up producing fewer (and less effective) terpenes than plants grown “in the wild.”
Some other plants also produce terpenes to attract pollinators, such as birds and bees. However, since cannabis itself is wind-pollinated, this isn’t something it needs to worry about (as if plants could worry in the first place).
To be honest, it might be easier to make a list of plants that don’t contain terpenes as opposed to ones that do. As mentioned before, there are thousands upon thousands of terpenes floating through the ether — scientists are constantly discovering new ones, as well — and they can be found in everything from the mightiest oaks to the tiniest blades of lemongrass.
To make things somewhat simpler, though, here’s a far-from-exhaustive list of where you can find terpenes aside from cannabis:
Pine trees might be the most famous producers of terpenes among this class of plants (in fact, they even lend their name to one of the most prominent terpenes, which we’ll discuss later), but they’re not the only ones. Cedars, firs, and birch trees are also known to be rich in terpenes — which is one of the reasons why forest bathing (literally, taking baths in a pool of water surrounded by trees) is believed to be so beneficial for human health.
Many citrus fruits like oranges and lemons are chock-full of terpenes (which makes sense, considering how distinctive their scents can be). Terpenes are also found in grapes and apples, among others, but one of their most interesting fruit-related sources might be mangoes — there’s a popular-but-unsubstantiated theory that mangoes intensify the effects of cannabis due to their high concentrations of a certain terpene.
As with fruits, terpenes can be found in vegetables of all shapes and sizes. Despite their dissimilarities, broccoli, corn, and sweet potatoes all feature terpenes of various types and concentrations. Green, leafy vegetables are believed to be an especially abundant source of terpenes, as if you needed one more reason to feel guilty for not eating enough salads.
Herbs and Spices
Since herbs and spices are often used to add a little extra flavor to your favorite dishes, you might expect them to be full of terpenes — and you’d be right. Black pepper, coriander, peppermint, thyme, basil, and cloves are just a handful of examples. An exhaustive list could go on for pages: Allspice, bay leaves, chives, dill, garlic … you get the idea.
While it’s nice to know that terpenes are all around us — and you don’t need to be a stoner to appreciate them — we’re guessing that you didn’t come here to learn about the benefits of forest bathing or the subtleties of plant growth cycles.
So let’s get down to the main event: Understanding why terpenes matter to cannabis specifically.
As with other plants, terpenes give cannabis its distinctive smell and taste — which can vary significantly from strain to strain. At the moment, these are the only effects of terpenes on cannabis that scientists have confirmed, but some experts are beginning to believe that they could be capable of much more.
For example, some terpenes are believed to accentuate the “couch lock” effect of certain cannabis strains: In other words, they boost the sedative properties of the strain, making it more effective for people dealing with insomnia. Other terpenes are believed to hold potent anti-anxiety abilities, which could make them beneficial in counteracting the paranoia-inducing effects of THC.
According to “the entourage effect,” a theory first introduced in the late 1990s by the legendary cannabis researcher Dr. Raphael Mechoulam, the various compounds found in cannabis (especially terpenes and cannabinoids, a class of chemicals that includes THC and CBD) work together to produce synergistic effects that heighten the potency of individual compounds.
While there’s still little scientific evidence to either support or refute this theory — though that could be changing in the near future as the U.S. federal government relaxes its restrictions on cannabis research — Mechoulam’s hypothesis has been championed by prominent cannabis scientists like Dr. Ethan Russo, perhaps the most outspoken advocate of the entourage effect today.
It’s one of the main reasons that full spectrum CBD oils are believed to be more effective than isolates, since full spectrum oils contain the plant’s full range of terpenes and cannabinoids as opposed to a single, “pure” ingredient. It also explains why some people are skeptical about odorless cannabis, since removing the plant’s odor would require removing its terpenes — which, as we’ll see shortly, could potentially have a number of beneficial effects.
Although there are at least 100 terpenes in cannabis (and possibly many more), only a handful of them are present in sufficient quantities to be of much concern. These are grouped into two main categories, primary and secondary terpenes.
As you might expect, primary terpenes tend to comprise a bigger percentage of a cannabis strain’s overall terpene profile, while secondary terpenes play a more supplemental role. There’s a great deal of dispute over the exact number of primary terpenes (and which ones should be considered as such), but generally speaking, many experts consider the following 10 terpenes to be “primary”:
Myrcene is the most prominent terpene in many cannabis strains — in some, it can comprise up to 65 percent of the overall terpene profile. It’s known for its earthy, musky scent.
Pinene is one of the most common terpenes in the world at large, and it’s also a key component of many cannabis strains. As its name suggests, this terpene has an odor reminiscent of pine trees. It comes in two varieties, known as alpha- and beta-pinene.
Humulene might be better known for its role in beer, but it’s also integral in cannabis. Its aroma is often described as “hopsy.”
Limonene is believed to be one of the most abundant terpenes in cannabis, with one study showing it makes up 16 percent of cannabis essential oil. If you’re thinking, “I bet it smells like lemons,” you would be right.
Linalool, sometimes regarded as the strongest-smelling cannabis terpene, is also the dominant terpene in lavender. Unsurprisingly, its scent is fresh, floral, and, well, lavender-y.
Also known as alpha-bisabolol, this terpene is widely used in beauty products. Many users describe its aroma as citrusy, peppery, or floral.
Yet another floral-scented terpene, terpineol also has notes of citrus. Aside from cannabis, it’s a major terpene in many other essential oils as well.
Valencene takes its name from Valencia oranges (the ones you’re supposed to juice, not eat), and it smells (and tastes) much like you’d expect it would.
Geraniol, which is the most prominent terpene in geraniums, is regarded by many as one of the best-smelling cannabis terpenes … perhaps because it reminds users of the flower.
While the cannabis industry has been quick to tout the miraculous power of terpenes (often by invoking studies that involve terpenes from non-cannabis sources), the jury is still out on whether cannabis provides these in sufficient quantities to yield results. Some companies, like True Terpenes, are now hard at work devising methods to synthetically produce terpenes for various medical applications — and “terpene-enhanced” cannabis products are likely to become a major trend in the coming months — but right now there’s more smoke than fire.
At the same time, the relative paucity of data doesn’t necessarily mean that terpenes are all hype and no substance when it comes to therapeutic potential. Here’s a selection of uses for which we have (at least some) scientific evidence:
A number of terpenes have shown the ability to reduce inflammation. In 2018, a study in the journal Cannabis and Cannabinoids Research showed that terpene-rich essential oils could decrease pain and inflammation in rats, though these were more effective for acute inflammation than chronic issues.
Limonene gets most of the buzz when it comes to anxiety-busting terpenes (a number of studies indicate it could increase the brain’s production of serotonin and dopamine), though caryophyllene and myrcene could also help in this regard thanks to their sedative properties.
Caryophyllene has also been shown to be effective at preventing scalp fungus and other types of fungal infections. Some scientists believe other terpenes such as limonene could have similar properties.
A number of terpenes, including terpineol and geraniol, were found to be highly effective against dangerous bacteria such as e. coli, according to a 2019 study in the journal Molecules.
While this might be one of the most controversial (and overemphasized) claims about terpenes, some studies have shown that terpenes like pinene, limonene, and humulene could be useful in treating certain forms of cancer. Take these claims with an extra grain of salt, though.
A surprising number of terpenes — including linalool, myrcene, and geraniol — have been linked with the ability to protect or repair damaged brain cells. In 2017, for example, a paper in the journal Evidence-Based Complementary and Alternative Medicine found that linalool “could be a potential agent for improving cognitive impairment in [people with Alzehimer’s disease].”
For the most part, terpenes have a positive safety profile — no studies have linked them with violent mood swings, organ failure, or other serious issues. However, there are a number of reasons to be cautious about them.
The first is allergies. Although terpene allergies are relatively rare, they do affect some people. According to a 2005 study in the journal Contact Dermatitis, linalool is the most common trigger for terpene-related allergies. It can induce reactions by coming in contact with the skin — which should give pause to anyone prone to allergies who uses cannabis topicals — or by being inhaled (though cannabis is less likely to trigger adverse reactions than other sources of linalool, like perfumes).
Another potential area of concern when it comes to terpenes relates to their chemical degradation when vaporized or dabbed. A 2017 study in the journal ACS Omega found that certain terpenes, such as myrcene, could create potentially harmful substances when exposed to extreme heat — which users then inhale directly into their lungs.
Although the study stopped short of suggesting terpenes are dangerous, their growing prevalence in many cannabis products has worried some experts. While the terpene content of most cannabis strains is around 2 percent, some companies are now “super-sizing” their products’ helping of terpenes up to 20 percent.
For Amber Wise, the scientific director of a cannabis testing lab in Washington, this is cause for alarm. “We don’t know anything about vaping terpenes or the degradation products that they might form after high heat exposure,” she told Chemical & Engineering News.
So while terpenes may hold a lot of promise for medicinal cannabis users, they also come with some warning signs — and who knows what the science may reveal in the days to come?