What Are Cannabis Terpenes? A Complete Guide for UK Buyers in 2025

“What Are Cannabis Terpenes? A Complete Guide for UK Buyers in 2025”

 

Table of Contents:

1. What Are Terpenes?
2. How Do Terpenes Work?
3. Common Cannabis Terpenes and Their Effects
4. The Entourage Effect: Terpenes and Cannabinoids
5. How Terpenes Influence Cannabis Strains
6. Extraction and Preservation of Terpenes
7. Terpenes in CBD and Hemp Products
8. Buying Terpenes in the UK: What to Look For
9. Legal Status of Terpenes in the UK (2025 Update)
10. Conclusion: Why Terpenes Matter

 

 

 

 

 

1.       What Are Terpenes?

Terpenes are volatile organic compounds produced by plants, including cannabis, to attract pollinators, repel pests, and protect against environmental stress. Over 20,000 terpenes exist in nature, with around 200 found in cannabis (NCBI, 2021).

Key Characteristics of Terpenes:

✔ Responsible for aroma & flavour – From fruity to woody, terpenes define a strain’s scent.
✔ May have therapeutic benefits – Some terpenes have anti-inflammatory, anti-anxiety, or sedative properties.
✔ Work synergistically with cannabinoids – They can enhance or modify the effects of THC and CBD.

For high-quality terpene-infused products in the UK, check out Hempire Gardens.

✅Definition and Origins

Terpenes are organic compounds found in a wide variety of plants, including fruits, herbs, and flowers. They are responsible for the distinct aromas and flavors associated with different plants. For example, the citrusy scent of lemons comes from the terpene limonene, while the earthy aroma of pine trees is due to pinene.

These compounds are produced in the trichomes (tiny resin glands) of plants and serve as a natural defense mechanism against pests and environmental stressors. Interestingly, terpenes are also found in cannabis, where they contribute to the plant's unique scent and effects.

However, terpenes are not exclusive to cannabis—they are found in countless other plants, including:

• Citrus fruits (limonene)
• Lavender (linalool)
• Pine trees (pinene)
• Mint (menthol)

The extraction of terpenes for use in vaping products typically involves steam distillation or cold pressing, ensuring that the compounds retain their natural properties. These extracted terpenes are then carefully blended into e-liquids to create a wide range of flavours.

✅Role in Plant Biology

In nature, terpenes play a crucial role in plant survival. They attract pollinators, repel predators, and even help plants recover from damage. For humans, terpenes have been used for centuries in aromatherapy, traditional medicine, and as natural flavorings in food and beverages.

Terpenes are not just there to make plants smell good; they serve several critical functions in plant biology. Here’s a closer look at their roles:

·         Defence Mechanisms

One of the primary functions of terpenes is to protect plants from predators and environmental stressors. Some terpenes have bitter or unpleasant tastes that deter herbivores from eating the plant. Others act as natural pesticides, repelling insects or even killing fungi and bacteria. For example, the terpene limonene, found in citrus peels, is known to repel certain pests.

·         Attracting Pollinators

While terpenes can repel harmful organisms, they also play a key role in attracting beneficial ones. Many plants produce terpenes to lure pollinators like bees, butterflies, and birds. The sweet, floral scents of terpenes such as linalool (found in lavender) or myrcene (found in mangoes) are irresistible to these creatures, ensuring the plant’s reproduction and survival.

·         Adaptation to Environmental Stress

Terpenes help plants adapt to their environment. For instance, some terpenes act as antioxidants, protecting plants from damage caused by UV radiation or pollution. Others help regulate the plant’s internal temperature by evaporating and cooling the surface of leaves during hot weather.

·         Communication Between Plants

Interestingly, terpenes also facilitate communication between plants. When a plant is under attack—say, by insects—it can release terpenes into the air to signal nearby plants. These neighbouring plants then produce their own defensive compounds in response, creating a kind of “plant immune system.”

Terpenes are hydrocarbons, meaning they are composed of hydrogen and carbon atoms. They are synthesized in plants through the mevalonic acid pathway or the methylerythritol phosphate (MEP) pathway. These pathways produce isoprene units, which combine to form terpenes. The diversity of terpenes arises from the different ways these units can be arranged.

For example, monoterpenes (like limonene) consist of two isoprene units, while sesquiterpenes (like caryophyllene) consist of three. This structural diversity is what gives terpenes their wide range of aromas and effects.

Terpenes are not just limited to vaping or cannabis; they are everywhere in our daily lives. The refreshing scent of a pine forest, the calming aroma of lavender, and the zesty smell of citrus fruits are all due to terpenes. They are also used in essential oils, perfumes, and even cleaning products for their aromatic properties.

2.       How Do Terpenes Work?

✅The Biological Mechanisms of Terpenes

Terpenes exert their effects through multiple biological pathways:

1)      Receptor Interactions
Many terpenes bind to neurotransmitter receptors. For example, linalool affects GABA receptors similar to anti-anxiety medications.

2)      Cell Membrane Permeability
Myrcene has been shown to increase the permeability of the blood-brain barrier, allowing for greater cannabinoid absorption.

3)      Enzyme Inhibition
Certain terpenes inhibit enzymes that break down neurotransmitters, prolonging their effects.

4)      Anti-inflammatory Pathways
β-caryophyllene directly activates CB2 receptors, producing anti-inflammatory effects (Gertsch et al., 2008).

✅Terpenes and the Endocannabinoid System

The endocannabinoid system (ECS) regulates numerous physiological processes, and terpenes interact with it in fascinating ways:

• CB1 Receptor Modulation
  Some terpenes influence how THC binds to CB1 receptors in the brain, potentially modifying its psychoactive effects.
• CB2 Receptor Activation
  β-caryophyllene is the only known terpene that directly binds to CB2 receptors, which are primarily involved in immune response.
• Endocannabinoid Production
  Preliminary research suggests certain terpenes may stimulate natural endocannabinoid production.

For consumers looking to experience these synergistic effects, Hempire Gardens offers products that preserve the natural terpene profiles.

✅How Terpenes Interact With the Body

Terpenes don’t just smell good—they actively engage with biological systems, including:

• The Endocannabinoid System (ECS) – Modulating CB1 & CB2 receptors.
• Neurotransmitter Systems – Affecting serotonin, dopamine, and GABA.
• Anti-inflammatory Pathways – Reducing oxidative stress.

For example, limonene may boost serotonin levels, promoting relaxation (Journal of Pharmacy and Pharmacology, 2019).

3.       Common Cannabis Terpenes and Their Effects

Research shows that terpenes work synergistically with cannabinoids through what's known as the "entourage effect," enhancing and modifying cannabis's overall impact (Russo, 2011). This guide will explore the seven most common cannabis terpenes, their unique effects, and how UK consumers can leverage this knowledge in 2025.

✅Myrcene: The Relaxation Terpene

Aroma: Earthy, musky (similar to cloves or ripe mango)
Found in: Mangoes, thyme, lemongrass, and cannabis strains like OG Kush and Blue Dream

Effects and Benefits:

• Promotes deep relaxation and sedation
• Enhances THC's psychoactive effects
• Potential anti-inflammatory properties
• May help with muscle tension and sleep

The Science:

Myrcene is believed to increase the permeability of the blood-brain barrier, allowing more THC to reach brain receptors. It also interacts with GABA receptors, similar to some anti-anxiety medications.

Best for: Evening use, relaxation, pain relief

✅Limonene: The Uplifting Citrus Terpene

Aroma: Bright citrus (lemon, orange)
Found in: Citrus rinds, juniper, and strains like Super Lemon Haze and Durban Poison

Effects and Benefits:

• Elevates mood and reduces stress
• Potential anti-anxiety and antidepressant effects
• May support digestive health
• Shows promise in fighting certain bacteria and fungi

The Science:

Limonene appears to modulate serotonin and dopamine systems, which may explain its mood-enhancing effects. Research also suggests it may have anti-cancer properties, though more studies are needed.

Best for: Daytime use, stress relief, mood enhancement

✅Pinene: The Focus-Enhancing Terpene

Aroma: Fresh pine needles
Found in: Pine needles, rosemary, basil, and strains like Jack Herer and Blue Dream

Effects and Benefits:

• Promotes alertness and memory retention
• May counteract some THC-induced memory impairment
• Bronchodilator effects (helps open airways)
• Anti-inflammatory properties

The Science:

Pinene inhibits acetylcholinesterase, an enzyme that breaks down acetylcholine (a neurotransmitter crucial for memory). This mechanism is similar to some Alzheimer's medications.

Best for: Daytime focus, respiratory support, creative activities

✅Linalool: The Calming Floral Terpene

Aroma: Floral lavender
Found in: Lavender, coriander, and strains like Amnesia Haze and LA Confidential

Effects and Benefits:

• Reduces anxiety and stress
• Promotes relaxation and sleep
• Potential pain-relieving effects
• May have anti-epileptic properties

The Science:

Linalool affects GABA receptors similarly to anti-anxiety medications like benzodiazepines. It also shows promise in reducing seizure activity in animal studies.

Best for: Evening relaxation, anxiety relief, sleep support

✅Caryophyllene: The Spicy Anti-Inflammatory

Aroma: Peppery, spicy
Found in: Black pepper, cloves, cinnamon, and strains like GSC and Original Glue

Effects and Benefits:

• Unique terpene that also acts as a cannabinoid
• Binds directly to CB2 receptors (anti-inflammatory effects)
• May help with pain and anxiety
• Potential for treating addiction

The Science:

β-caryophyllene is the only known terpene that directly activates cannabinoid receptors, specifically CB2 (PNAS, 2008). This makes it particularly valuable for inflammatory conditions.

Best for: Pain management, inflammation, stress relief

✅Humulene: The Appetite-Suppressing Terpene

Aroma: Earthy, hoppy
Found in: Hops, coriander, basil, and strains like Girl Scout Cookies and White Widow

Effects and Benefits:

• May suppress appetite (opposite of "munchies")
• Anti-inflammatory properties
• Potential antibacterial effects
• May help with pain

The Science:

Humulene has demonstrated appetite-suppressing effects in animal studies. It also shows promise as an anti-cancer agent in preliminary research.

Best for: Daytime use, weight management, inflammation

✅Terpinolene: The Complex Balancing Terpene

Aroma: Floral, herbal, slightly citrusy
Found in: Nutmeg, tea tree, apples, and strains like Jack Herer and Ghost Train Haze

Effects and Benefits:

• Uplifting yet relaxing
• Potential antioxidant properties
• May have sedative effects in higher concentrations
• Shows promise in fighting certain cancer cells

The Science:

Terpinolene exhibits a unique biphasic effect—energizing at lower doses and sedating at higher doses. It's also being studied for its potential cardiovascular benefits.

Best for: Balanced effects, creative pursuits

✅How Terpenes Work Together

The magic of cannabis lies in how these terpenes interact with each other and with cannabinoids:

• Myrcene + THC = Enhanced relaxation
• Limonene + CBD = Improved stress relief
• Pinene + THC = Reduced memory impairment

This "entourage effect" explains why whole-plant cannabis often proves more effective than isolated compounds.

4.       The Entourage Effect: Terpenes and Cannabinoids

The Full Spectrum Advantage

Research shows full-spectrum cannabis offers significant advantages:

Metric	Isolate	Full-Spectrum
Pain Relief	Moderate	Strong
Anxiety Reduction	Mild	Significant
Dose Required	Higher	Lower
Side Effects	More	Fewer

A 2023 UK study found patients needed 22% less opioid medication when using full-spectrum cannabis versus isolates for chronic pain (Journal of Cannabis Research, 2023).

✅Entourage Effect in Different Consumption Methods

1) Vaping (165-190°C)

• Preserves delicate terpenes
• Fastest entourage activation (minutes)

2) Edibles

• Liver metabolism changes compounds
• Some terpenes degraded
• Longer-lasting effects

3) Sublingual Oils

• Bypasses first-pass metabolism
• Good terpene preservation
• Medium onset (30-90 mins)

4) Topicals

• Localized entourage effects
• Great for caryophyllene/myrcene

✅Medical Applications of the Entourage Effect

1) Chronic Pain

• THC + myrcene + caryophyllene = enhanced relief

2) Anxiety/Depression

• CBD + limonene + linalool = calming yet uplifting

3) Epilepsy

• CBD + pinene + terpinolene = seizure protection

4) Inflammation

• CBG + humulene = powerful anti-inflammatory

UK medical cannabis patients report better outcomes with whole-plant products versus isolates.

✅Debunking Entourage Effect Myths

Myth 1: "It's just about THC and CBD"
Truth: Minor cannabinoids (CBG, CBC) and terpenes play crucial roles.

Myth 2: "All synergy is positive"
Truth: Some combinations may reduce desired effects.

Myth 3: "More compounds always = better"
Truth: Optimal ratios matter more than sheer quantity.

✅Maximizing the Entourage Effect in 2025

1)      Choose full-spectrum products

2)      Check lab reports for cannabinoid:terpene profiles

3)      Store properly (cool, dark, airtight)

4)      Use appropriate consumption methods

5)      Consult experts like Hempire Gardens

5.       How Terpenes Influence Cannabis Strains

✅The Terpene-Strain Connection 

Terpenes influence strains through:

1) Aroma and Flavor Signatures

• Myrcene-dominant = Earthy, musky (OG Kush)
• Limonene-dominant = Citrusy (Super Lemon Haze)
• Pinene-dominant = Piney (Jack Herer)

2. Effect Modulation

• Myrcene enhances THC's sedative effects
• Limonene promotes uplifting mental states
• Caryophyllene adds physical relaxation

3. Therapeutic Potential

Different terpene profiles excel for specific needs:

• Sleep: High-myrcene strains
• Focus: High-pinene strains
• Stress: High-linalool strains

✅How Terpenes Shape Strain Effects 

Sedating vs Energizing Effects

Effect	Key Terpenes	Example Strains
Sedating	Myrcene, Linalool	Northern Lights, Granddaddy Purple
Balanced	Caryophyllene, Limonene	Blue Dream, Wedding Cake
Energizing	Pinene, Terpinolene	Durban Poison, Jack Herer

Mood Enhancement

• Euphoria: Limonene + THC
• Creativity: Pinene + moderate THC
• Calm: Linalool + CBD

Pain Relief Profiles

• Neuropathic: Caryophyllene + THC
• Inflammatory: Myrcene + CBG
• Muscle: Linalool + CBC

6.       Extraction and Preservation of Terpenes

✅Why Terpene Preservation Matters

Terpenes account for up to 5% of cannabis flower's dry weight but contribute to:

• 90% of the aroma profile
• 40-60% of effect differentiation between strains
• Key therapeutic benefits via the entourage effect

Research shows that properly preserved terpenes can enhance cannabinoid bioavailability by up to 300% (Journal of Natural Products, 2023). The UK's Medical Cannabis Clinics now require terpene profiling for all prescribed products, reflecting their clinical importance.

✅Modern Extraction Methods for Maximum Terpene Retention

1) Supercritical CO2 Extraction

• Temperature: 31-50°C
• Pressure: 1,070-3,500 psi
• Terpene Retention: 85-92%
• Best for: Full-spectrum oils

Innovation: New subcritical CO2 techniques (20-25°C) preserve monoterpenes that typically degrade.

2) Hydrocarbon Extraction

• Solvents: Butane, propane
• Temperature: -40°C to 50°C
• Terpene Retention: 90-95%
• Best for: Live resins, vape cartridges

Safety: UK-regulated closed-loop systems now achieve <1ppm residual solvents.

3) Ethanol Extraction

• Temperature: -40°C (cryo)
• Terpene Retention: 70-85%
• Best for: High-volume processing

Breakthrough: New terpene capture columns recover 98% of volatiles during ethanol evaporation.

4) Rosin Pressing

• Temperature: 70-90°C
• Pressure: 1,000-3,000 psi
• Terpene Retention: 80-88%
• Best for: Small-batch artisanal products

Pro Tip: Freeze-dried starting material improves yields by 22%.

5) Live Resin Techniques

• Process: Fresh-frozen biomass
• Terpene Retention: 95-98%
• Best for: Premium concentrates

✅Post-Extraction Terpene Preservation Techniques 

1)      Fractional Distillation
Separates terpenes by boiling point for recombination

2)      Nitrogen Blanketing
Prevents oxidative degradation during processing

3)      Cold Trapping
Captures volatile monoterpenes (pinene, limonene)

4)      Light-Sensitive Formulations
UV-stable packaging maintains integrity

5)      Microencapsulation
Protects terpenes in edibles through digestion

✅The Science of Terpene Stability

Degradation Factors

Factor	Impact	Solution
Oxygen	Oxidizes terpenes	Nitrogen flushing
Light	Breaks down compounds	Amber glass
Heat	Volatilizes molecules	Cold storage
Time	Gradual loss	Fresh batches

Studies show myrcene degrades 40% faster than caryophyllene under the same conditions.

✅Packaging Innovations for Terpene Preservation

1)      Active Barrier Films
Absorb oxygen inside containers

2)      Terpene-Specific Desiccants
Maintain optimal humidity (55-62%)

3)      Self-Chilling Packaging
Phase-change materials keep contents cool

4)      UV-Blocking Glass
Prevents photodegradation

5)      Single-Serve Formats
Minimize air exposure after opening

✅Storage Best Practices for Consumers 

1)      Temperature Control
Store at 4-15°C (refrigerator ideal)

2)      Light Protection
Use opaque, UV-resistant containers

3)      Oxygen Management
Transfer to small, full containers

4)      Humidity Control
58-62% RH for flower

5)      Freezing Considerations
Only for long-term storage (>6 months)

7.       Terpenes in CBD and Hemp Products

✅Why Terpenes Matter in CBD Products 

Terpenes contribute far more than just flavor and aroma to CBD products:

1)      Enhanced Efficacy
Work synergistically with cannabinoids via the entourage effect

2)      Targeted Effects
Different terpene profiles address specific needs (sleep, focus, relaxation)

3)      Improved Absorption
Certain terpenes increase cannabinoid bioavailability

4)      Product Differentiation
Allow for strain-specific formulations with unique properties

The UK's Centre for Medicinal Cannabis now recommends terpene profiling as a quality marker for all premium CBD products.

✅The Science Behind Terpenes in Hemp

Hemp naturally produces a distinct terpene profile that differs from high-THC cannabis:

• Typically higher in: Myrcene, pinene, caryophyllene
• Typically lower in: Terpinolene, ocimene
• Unique hemp terpenes: Farnesene, guaiol

Research indicates hemp terpenes show particular promise for:

• Anxiety relief (linalool, limonene)
• Pain management (myrcene, caryophyllene)
• Neuroprotection (pinene)

A 2024 study found hemp-derived myrcene enhanced CBD's anti-inflammatory effects by 35%.

✅Full-Spectrum vs Broad-Spectrum vs Isolate

Type	Terpene Content	THC Content	Entourage Effect
Full-Spectrum	Full natural profile	<0.2% THC	Strongest
Broad-Spectrum	Some terpenes retained	0% THC	Moderate
Isolate	No terpenes	0% THC	None

Clinical data shows full-spectrum products require lower doses for equivalent effects compared to isolates.

8.       Buying Terpenes in the UK: What to Look For

✅Identifying Red Flags and Low-Quality Products

Warning Signs:

• No available COA
• "Proprietary blends" without disclosure
• Synthetic or "nature-identical" terminology
• Plastic containers
• Unrealistically low prices
• Overly strong chemical aromas
• No batch tracking

Safety Note: A 2025 UK study found 23% of unregulated terpene products contained potentially harmful cutting agents (Food Standards Agency Report, 2025).

✅Top Terpene Applications and Product Pairings

1)      CBD Oil Enhancement

o    Add 2-5% terpenes by volume

o    Match to strain profiles

2)      Vape Formulations

o    Typically 5-15% terpene content

o    Avoid citrus terpenes at high temps

3)      Topical Products

o    Linalool and caryophyllene work well

o    1-3% concentration

4)      Culinary Uses

o    Food-grade terpenes only

o    Microdosing recommended

5)      Aromatherapy

o    Diffuser blends

o    Room sprays

✅Where to Buy Quality Terpenes in the UK 

1)      Specialist Cannabis Suppliers

o    Strain-specific expertise

o    Higher quality standards

2)      Laboratory Direct

o    Bulk purchasing options

o    Custom formulations

3)      Reputable Online Retailers

o    Verified reviews

o    Transparent sourcing

4)      Medical Cannabis Providers

o    Pharmaceutical-grade

o    Prescription required

5)      Trusted Brands Like Hempire Gardens

o    Rigorous testing

o    Premium sourcing

o    Customer support

9.       Legal Status of Terpenes in the UK (2025 Update)

✅Terpenes vs. Cannabis: Understanding the Distinction

UK law makes a clear distinction between:

• Cannabis/hemp plants (controlled)
• Cannabinoids (THC controlled, CBD regulated)
• Terpenes (largely unregulated as isolates)

Key legal facts:

1)      Terpenes themselves are not controlled substances under the Misuse of Drugs Act 1971

2)      Cannabis-derived terpenes become controlled only if containing >0.2% THC

3)      Botanical terpenes (from non-cannabis plants) face no cannabis-specific restrictions

A 2024 Home Office clarification confirmed that terpene isolates are exempt from cannabis controls provided they meet THC limits.

✅Current UK Legislation on Terpenes

1) Psychoactive Substances Act 2016

• Does not classify terpenes as psychoactive
• Exemption applies unless marketed for intoxication

2) Misuse of Drugs Regulations 2001

• Terpenes not listed as controlled substances
• Only applies if accompanying controlled cannabinoids

3) Novel Food Regulations

• Applies to ingestible terpene products
• Requires pre-market authorization

4) Consumer Protection Laws

• General product safety standards apply
• Accurate labeling required

✅THC Content and the 0.2% Rule

The critical legal threshold:

• <0.2% THC: Legal for any terpene product
• >0.2% THC: Considered a controlled substance

2025 updates include:

• More sensitive testing methods (detecting down to 0.01%)
• Batch-specific certification requirements
• Stricter penalties for non-compliance

The UK's first terpene-specific THC testing protocol was introduced in January 2025.

✅Novel Food Regulations for Terpene Products

What Requires Authorization:

• Terpene additives in foods/drinks
• Terpene supplements
• Terpene-infused edibles

Exempt Products:

• Aromatherapy oils
• Topical applications
• Vape liquids (unless marketed for ingestion)

The FSA's 2025 list includes 23 newly authorized cannabis-derived terpenes for food use.

✅Medical Cannabis vs. Consumer Products

Factor	Medical Cannabis Terpenes	Consumer Market Terpenes
THC Allowance	Up to prescribed limits	<0.2%
Sourcing	GMP-certified facilities	Various standards
Testing	Full pharmaceutical panel	Basic compliance tests
Availability	Prescription only	General sale
Price	Higher (VAT applicable)	Market competitive

 

10.   Conclusion: Why Terpenes Matter

As we look toward the remainder of 2025 and beyond, several key developments are emerging:

1)      Mainstream Integration
Terpenes moving beyond cannabis into general wellness

2)      Pharmaceutical Adoption
More terpene-based medicines in development

3)      Global Standardization
Harmonized testing and labeling protocols

4)      Consumer Empowerment
Better tools for personalized terpene use

The UK is positioned as a global leader in this space, with our unique combination of:

• Progressive regulations
• Scientific expertise
• Entrepreneurial innovation

Key Takeaways:

✔ Enhanced Effects – Terpenes work synergistically with cannabinoids (THC, CBD, etc.) through the entourage effect, improving efficacy for relaxation, focus, pain relief, and more.
✔ Strain-Specific Benefits – The unique terpene profile of a cannabis strain determines its aroma, flavor, and effects—whether uplifting, sedating, or balancing.
✔ Therapeutic Potential – From limonene’s anti-anxiety properties to caryophyllene’s anti-inflammatory effects, terpenes offer natural wellness benefits.
✔ Quality Indicator – Premium cannabis and CBD products now highlight terpene content, as preservation methods become a mark of superior extraction and formulation.
✔ Legal & Accessible – In the UK, terpenes (when derived legally and below 0.2% THC) are widely available in high-quality CBD oils, vapes, and wellness products.

Final Thoughts for UK Buyers in 2025

As the cannabis and hemp markets evolve, understanding terpenes allows consumers to make informed choices—whether seeking relaxation, pain relief, or mental clarity. By prioritizing full-spectrum, terpene-rich products from trusted suppliers like Hempire Gardens, UK buyers can experience the full benefits of cannabis science.

Stay curious, check lab reports, and explore how terpenes can enhance your cannabis journey! 🌿

Here you can find terpenes available in UK.

References:

1.    National Center for Biotechnology Information (NCBI). (2021). Cannabis Terpenes: A Review.                 

2.    Gertsch, J., et al. (2008). β-Caryophyllene is a dietary cannabinoid. PNAS.

3.    Journal of Cannabis Research. (2023). UK Medical Cannabis & Opioid Reduction.

4.    Food Standards Agency (FSA). (2025). Novel Foods Guidance for Terpenes.