Full spectrum RSO (Rick Simpson Oil) is a thick, dark cannabis extract that contains the entire range of compounds found in the plant, including cannabinoids, terpenes, flavonoids, and plant waxes. Unlike refined cannabis products that isolate one or two compounds, RSO preserves everything the plant produces in a single, highly concentrated oil. A typical syringe holds about 1 gram and contains 600 to 800 mg of THC, making it one of the most potent cannabis products available.
The oil is named after Rick Simpson, a Canadian engineer who reportedly used a homemade cannabis extract to treat basal cell skin cancers on his arm in the early 2000s. Simpson then became a vocal advocate for whole-plant cannabis extraction, sharing his method freely. His core philosophy was simple: don’t isolate a single chemical like pure THC, but capture everything the plant has to offer in one extract. That whole-plant approach is what makes RSO “full spectrum.”
What Makes RSO “Full Spectrum”
The term full spectrum means the oil retains the complete chemical profile of the cannabis plant rather than zeroing in on one compound. THC is the most abundant cannabinoid, but the extract also carries CBD, CBG, CBN, CBC, and many others in smaller amounts. Beyond cannabinoids, RSO holds onto terpenes (aromatic oils like myrcene, limonene, and pinene), flavonoids (plant pigments with antioxidant properties), chlorophyll, and natural waxes. This is why RSO has its characteristic dark green or almost black color and a strong, earthy taste.
Flavonoids called cannflavins, which have anti-inflammatory and antioxidant properties, are a good example of what sets full spectrum apart. These compounds are largely absent in purified extracts but remain intact in RSO. The same goes for many minor cannabinoids that exist in trace amounts. None of these would survive the heavy refinement used to produce distillate or isolate products.
The Entourage Effect
The main argument for full spectrum extraction is something called the entourage effect. The idea is that cannabis compounds work together synergistically, producing stronger or more nuanced effects than any single compound on its own. This isn’t just about multiple compounds hitting the same target in your body. The interactions happen in several ways at once.
CBD, for instance, slows the liver’s conversion of THC into a more potent psychoactive form (11-OH-THC) by inhibiting certain liver enzymes. CBD also acts as a negative modulator at the same brain receptors THC activates, which can temper THC’s intensity. On the terpene side, certain aromatic compounds in cannabis can enhance the ability of cannabinoids to cross the blood-brain barrier, effectively improving how well they’re absorbed. Other compounds may block drug efflux transporters, which are cellular mechanisms that pump substances back out of cells before they can take effect.
The practical result, according to researchers reviewing the available evidence, is that the whole extract can produce effects that are qualitatively different from what any single purified cannabinoid delivers. This is a key reason medical cannabis users often seek out RSO specifically.
How RSO Is Made
The extraction process is straightforward compared to other cannabis concentrates. Cannabis flower is soaked in a solvent, most commonly ethanol, which strips the cannabinoids, terpenes, and other compounds from the plant material. The plant matter is then filtered out, and the remaining liquid is gently heated to evaporate the solvent, leaving behind the thick, tar-like oil.
Rick Simpson’s original method called for pure light naphtha as the solvent, though ethanol has become the standard in commercial production because of its safety profile and scalability. Some producers use isopropyl alcohol. The choice of solvent matters because it affects which compounds end up in the final product. Ethanol is particularly effective at pulling a wide range of polar and nonpolar compounds, which is why it captures chlorophyll (giving the oil its dark color) along with the desired cannabinoids and terpenes. Commercial RSO typically lands in the 40 to 60% cannabinoid concentration range as a crude extract, though some products test higher.
Because RSO is a crude extract with minimal post-processing, it looks and feels very different from the golden, translucent oils you might see in vape cartridges. That lack of refinement is intentional. The dark color, strong flavor, and thick consistency are signs that the full chemical profile has been preserved.
Potency and Dosing
RSO is exceptionally strong. With THC content often exceeding 70%, even a tiny amount delivers a significant dose. This is why the standard advice for new users is to start with about half a grain of rice worth of oil, taken three times a day. That tiny bead of oil is enough to produce noticeable effects for someone without a high tolerance.
The typical protocol involves doubling the dose every four days, which gives your body time to build some tolerance to the psychoactive effects. It takes most people three to five weeks to work up to a full gram per day, which equals roughly 8 to 9 rice-grain-sized drops every eight hours. Many people never reach or need that full gram. The gradual approach helps avoid the intense sedation and disorientation that can come from taking too much THC at once.
RSO is most commonly taken orally, either placed directly under the tongue, swallowed on its own, or mixed into food. Some people apply it topically. It is not designed for smoking or vaping, particularly if it was made with solvents that may not be safe to inhale.
What People Use It For
RSO is most popular among people dealing with chronic pain, cancer-related symptoms, multiple sclerosis, severe insomnia, and appetite loss. Its high THC concentration and full spectrum profile make it appealing for conditions that haven’t responded well to milder cannabis products or single-cannabinoid formulations.
Users frequently report that RSO helps with sleep and appetite. Its sedating quality, while sometimes unwelcome during the day, makes it particularly useful as a nighttime option for people struggling with insomnia or pain that disrupts sleep. Some chronic pain patients have reported using RSO to reduce their dependence on opioid medications for breakthrough pain, though individual results vary widely.
It’s worth noting that Rick Simpson’s original claims about RSO curing cancer have not been validated in clinical trials. While some cannabinoids have shown anticancer activity in lab and animal studies, there is no established evidence that RSO can replace conventional cancer treatment.
RSO vs. Distillate
The easiest way to understand RSO is to compare it with distillate, which sits at the opposite end of the cannabis extract spectrum. Distillate is made through short-path distillation, a process that separates cannabinoids from everything else at carefully controlled temperatures. The result is a clear, nearly odorless oil that can reach 95 to 99% pure THC or CBD. It’s clean, consistent, and versatile, but most terpenes and minor cannabinoids are stripped away during refinement.
RSO sacrifices that purity and polish to keep the full plant profile intact. Where distillate offers precise, predictable dosing of a single cannabinoid, RSO delivers a more complex chemical experience. People who want maximum medicinal breadth tend to choose RSO. Those who prefer clean flavor, exact dosing, or want to avoid the strong earthy taste of whole-plant extract often prefer distillate. Neither is inherently better; they serve different purposes.
Storage and Shelf Life
RSO is remarkably stable when stored properly. Kept in a dark glass container in a cool environment, it can last up to 10 years. Heat, light, and air exposure are the main enemies, as they degrade cannabinoids and terpenes over time. Most people store their RSO syringes in a refrigerator, which also makes the thick oil easier to manage by keeping it firm. If it becomes too stiff to dispense, briefly warming the syringe between your hands or running it under warm water softens it enough to squeeze out a dose.