Short answer
RSO stands for Rick Simpson Oil. It is a dark, sticky, full-extract cannabis oil that is usually high in THC and low in CBD. The marijuana part of the name matters. Most real RSO comes from drug-type cannabis rather than hemp, so it does not sit on CBD store shelves in the US. THC content above 0.3% keeps it in state-licensed dispensaries, and it remains illegal under federal law.
Why it is called RSO
The name comes from Rick Simpson, a Canadian who started promoting a homemade cannabis extract in the mid 2000s after using it on a skin problem. He later pushed it as a cancer treatment and posted directions for making it at home with a solvent. Those claims never went through clinical trials, and no health agency recognizes RSO as a cancer therapy. The nickname stuck anyway.
Weed RSO Oil: What It Is and How It Compares to CBD
How the oil is made
The general process is easy to describe and risky to do. Cannabis plant material is washed with a solvent such as ethanol. The solvent is then evaporated off, leaving a decarboxylated oil behind. Decarboxylation is the heat step that converts THCA into THC, which is why RSO hits hard when you eat it. The finished product often runs 60 to 90 percent cannabinoids by weight, and THC is the main one.
Solvent extraction at home is a bad idea for most people. Ethanol and similar solvents are flammable, and a poorly vented kitchen is a fire hazard. Commercial producers use closed-loop equipment and lab testing that a home setup cannot match.
RSO vs CBD oil
These two get mixed up constantly, so here is the split.
- Plant source: RSO comes from high-THC cannabis. CBD oil usually comes from hemp.
- Main cannabinoid: THC for RSO. CBD for CBD oil, often with trace THC only.
- Effect: RSO is intoxicating. CBD is not.
- Where it is sold: RSO in dispensaries in legal states. CBD online, in pharmacies, and in retail shops.
- Dosing: RSO is a thick tar, so people warm it and measure out portions the size of a grain of rice. CBD oil is typically a dropper bottle with a marked dose.
Some hemp companies sell a CBD-rich extract they call RSO style. That is a marketing label. The chemistry is closer to a full spectrum CBD oil than to the original.
Legal status in the US
Any cannabis product over 0.3% delta-9 THC by dry weight is a Schedule I controlled substance under federal law. That covers standard RSO. State medical and adult-use programs allow it inside their borders, which is why you can buy it at a dispensary in some states and not others. Hemp-derived CBD, which has to stay under that THC threshold, sits in a different legal lane under the 2018 Farm Bill. Federal agencies still treat unapproved cannabis extracts as unapproved drugs.
What research supports
This is where the honest answer is short. The National Cancer Institute notes that cannabinoids have been studied for nausea, appetite, pain, and sleep in cancer patients, and that no cannabis product is FDA approved to treat cancer itself. The FDA has approved a small number of cannabinoid medicines, including synthetic THC products and a purified CBD drug for certain seizure disorders. RSO is not one of them. Stories about people curing tumors with oil are not evidence, and they can pull someone away from treatment that works.
If you are shopping
- Read the certificate of analysis for the batch, not just the front label.
- Check THC and CBD as separate numbers. A product sold as CBD with 30% THC is not what most buyers expect.
- Buy THC products only from a licensed dispensary in your state.
- For CBD, look for a supplier that posts third-party lab results and lists the full cannabinoid profile.
- Treat any product claiming to cure cancer as a red flag.
Safety notes
Oral THC is slow and uneven. Onset can take an hour or more, and people who re-dose too soon often end up anxious, dizzy, or nauseated. High doses can raise heart rate and trigger short-term paranoia. THC also interacts with some medications through liver enzymes, so check with a pharmacist if you take prescriptions. Start lower than you think you need, and keep it away from kids and pets.