Hemp, lemons, and oranges have something in common: they are rich in limonene, a beneficial terpene found in hemp and peels of citrus fruits that gives them their signature smell.
According to science, citrus smells such as orange and lemon can help reduce stress and nervous tension. So, if you’ve noticed that the scent of an orange (or hemp) makes you more relaxed, now you know your assumptions have been validated by science.
What is Limonene?
Limonene is a chemical compound, also known as a terpene, naturally found in the essential oils of various plants and fruits.
This aromatic compound is secreted alongside THC and CBD in the hemp plant and together with other terpenes determines the smell and flavor of the plant.
Limonene also has an important role in the overall healing benefits of the hemp plant.
When limonene and other terpenes and cannabinoids are taken together, they increase the healing power of hemp.
Natural sources of limonene
- Cannabis Sativa (hemp)
- Peel of citrus fruits, such as grapefruit, lemon, lime, mandarin and oranges in particular
- Fir needle
- Palo Santo
Limonene: Most Useful Terpene
Research studies on limonene indicate that this terpene shows the following properties:
Uses & Benefits of Limonene
Several animal studies showed that limonene reduced pain, sensitivity to pain, and widespread pain in bones and muscles in mice.
Both inhaled and as an aromatherapy agent, limonene reduced pain severity, nausea, vomiting in pregnant women.
Reduces Skin Inflammation
Usually, severe cases of skin diseases such as psoriatic arthritis don’t respond well to prescribed medication, so people are seeking natural alternatives.
Studies suggest that if applied topically, D-limonene can smooth aching, burning skin and improve wound-healing by reducing pro-inflammatory cytokine production (cells responsible for some dermatitis symptoms).
Relief from Heartburn and Gastric Reflux
In one human study, 19 people were given heartburn medications, 17 people noticed the heartburn symptoms were gone after taking only limonene once a day for two weeks.
Limonene coats the esophagus and may also help neutralize stomach acid. It also increases the production of gastric mucus to promote gut healing.
A study on healthy mice treated with limonene showed a significant increase in antibodies production when exposed to foreign antigens.
Limonene also stimulated the immune cells in the pancreas and intestines.
Limonene is a great natural alternative for relieving stress. Many inflammatory diseases originate from stress.
Stress also causes chronic pain, disbalance in the sleep cycle, accelerated aging and triggers the release of cortisol, the stress hormone that can disrupt the parasympathetic nervous system.
Several studies showed that this compound showcases anti-stress properties and reduces anxiety.
A study indicated that if inhaled, limonene reduced anxiety levels, which means it works well in aromatherapy.
Medicinal Uses of Limonene
Limonene shows many medicinal properties and can be used for alleviating symptoms of:
- Bronchitis and other respiratory infections
- Heart problems
D-Limonene vs. L-Limonene
Limonene is mainly formed in the sticky resin glands of plants and is subdivided into two stereo-isomers—same molecules with a different structure—that have their distinctive flavor:
- D-Limonene—found in large concentration in the essential oils of citrus fruits
- L-Limonene—found in pine, presents a turpentine aroma
How is limonene obtained? There are two methods used to obtain limonene from the peel of orange and both influence the amount of terpenes:
- Centrifugal separation—oil composed of 90% limonene
Steam distillation—lower percentage of limonene compared to first method
Studies on Limonene
Some of the known ways of how limonene produces its effects are:
- Anti-inflammatory effects: according to a study, limonene has mechanisms of action to reduce inflammation. 
- Antioxidant effects: an animal study showed that limonene suppressed the expression of genes that produce MMPs–proteins that break down the extracellular matrix–and also increased antioxidant levels. 
- Anti-anxiety effects: it is still unknown how limonene helps reduce anxiety, but the terpene interacts with 5-HT1A receptors, a neurotransmitter linked to anxiety and depression. 
- Stress-relieving effects: limonene and perillyl alcohol, the product of limonene breakdown can prevent overstimulation of HPA axis and reduce stress. 
- Limonene makes you less high: limonene can decrease the psychoactivity of THC in marijuana.
High Limonene Hemp Strains
Sour Space Candy Flower. With .05% limonene, Sour Space offers a unique flavor similar to sour candy.
Elektra CBD Hemp Flower.This strain contains .05% of limonene and is great for reducing pain and inflammation.
FAQ on Limonene
Limonene offers a lot of health benefits. This terpene shows anti-inflammatory, antifungal, antibacterial and antioxidant effects.
Several studies show the potential of limonene for alleviating symptoms in conditions such as anxiety and depression.
Limonene can also boost the immune system, help relieve pain, heartburn, damaged skin, reduce inflammation in the gut, dissolve gallstones and much more.
Yes, limonene is safe if taken in food amounts. No, Limonene is not a known carcinogen. Also, long-term, medicinal amounts of limonene administered orally for up to one year appears to be safe for most people.
Aside from few side-effects, such as skin irritation and nausea, d-limonene shows no serious risk. Limonene is considered a safe ingredient by the FDA.
D-limonene is considered a safe compound by the Food and Drug Administration (FDA), only if used in food amounts. Dosage is key in avoiding limonene side-effects, but limonene appears to be safe if used orally for up to a year. Possible side effects of limonene include:
- Skin irritation — may happen after long-term exposure of pure limonene on the skin.
- Nausea — if used in very high doses, limonene can cause nausea.
Limonene is used for various applications, including in foods, beverages, and chewing gum added for flavoring.
Other applications include aromatherapy for stress release, as well as medicinal uses to treat a cold, flu, bronchitis, sinusitis, and more.
Limonene can be used as a fragrance, paint remover, and added to cleaning products.
This terpene has evolved from geranyl pyrophosphate (GPP), also known as geranyl diphosphate (GDP) which is one of the two main components of alpha-pinene.
So, the biosynthesis starts with isopentenyl diphosphate (isopentenyl pyrophosphate or IPP) and dimethylallyl diphosphate (dimethylallyl pyrophosphate or DMAPP) being combined to form geranyl diphosphate.
Following a three-step route, geranyl diphosphate is cyclized to limonene.