AROMATHERAPY FOUNDATIONS by Primrose Apothecary lecture for Mountain Rose herbs
UNDERSTANDING ESSENTIAL OILS
Hello everyone, and welcome. My name is Felicia Howe, and I am the founder of Primrose Apothecary. I grow and cultivate over 60 flower essences through my small urban farm in Portland, Oregon. I am an herbalist, holistic aesthetician, and educator with more than 30 years of experience in health, beauty, and wellness. I am also an accredited, certified aromatherapist, and I have spent many years working with essential oils through case studies and practical aromatherapy. So, today I want to start with the foundation. Before we talk about individual oils and how they’re traditionally used, I want you to understand what an essential oil actually is. That's where responsible aromatherapy begins.
THE PURPOSE OF THIS CLASS
is designed to give you a practical foundation for working with essential oils safely and intentionally. I am not here to diagnose disease or make drug claims. And I am not here to tell you that essential oils are a magical cure for everything. Instead, I want you to leave understanding:
• where essential oils come from
• how they are produced
• why concentration matters
• what essential oils contain
• how chemistry influences their characteristics
• how scent interacts with the nervous system
• how to approach topical use responsibly
• how quality and sourcing affect the finished oil
• how to begin creating intentional blends
The most important principle is simple:
NATURAL DOES NOT AUTOMATICALLY MEAN SAFE.
Essential oils are natural materials—but they are also highly concentrated botanical extracts. The more concentrated something becomes, the more important it is to understand what we are working with. So WHAT IS AN ESSENTIAL OIL?
One of the first distinctions we need to make is between several different botanical preparations. They may all come from plants, but they are not interchangeable.
TINCTURE
A tincture is created by extracting plant material in a solvent, commonly a mixture of alcohol and water. The solvent draws out soluble constituents from the plant and also helps preserve the finished preparation. A tincture is an herbal extract, not an essential oil.
FLOWER ESSENCE
A traditional flower essence is prepared by placing flowers in water, often using sunlight as part of the preparation process. The plant material is removed, and the resulting preparation is preserved, commonly with alcohol. Flower essences are a distinct botanical preparation and should not be confused with essential oils or tinctures.
INFUSED OIL
An infused oil is created by placing botanical material into a fixed or carrier oil. I generally prefer dried herbs for infused oils because fresh plant material contains water, which can create stability and preservation challenges.
Infused oils are wonderful for:
• body oils
• facial oils
• balms
• salves
• massage
• botanical skincare
But an infused oil is not an essential oil.
An essential oil is a concentrated fraction of a plant’s volatile aromatic constituents. It is not simply the plant in liquid form. This distinction is fundamental. The most common method of producing essential oils is steam distillation. Water is heated to create steam. The steam passes through the plant material and carries volatile aromatic molecules. The vapor then moves into a condenser, where it cools and returns to a liquid state. The resulting distillate separates into essential oil and hydrosol. The aromatic water produced during distillation contains water-soluble constituents and very small amounts of volatile aromatic oil called hydrosols. Hydrosols are not simply leftover water. They are valuable botanical preparations in their own right and can be especially useful in skincare, facial mists, compresses, and other applications. Some essential oils, particularly many citrus oils, are produced through mechanical extraction rather than steam distillation.
This distinction matters because the extraction method can influence the chemistry and safety profile of the finished oil.
An essential oil may look like a tiny bottle of plant material, but that bottle represents a much larger quantity of botanical material. The amount required varies dramatically from plant to plant.
A BOTTLE OF ESSENTIAL OIL IS NOT THE EQUIVALENT OF HOLDING THE PLANT IN YOUR HAND.
It is a concentrated chemical fraction. That means our relationship to the material must change once the plant has been distilled or pressed. We are no longer working with a handful of lavender flowers. We are working with a concentrated mixture of volatile chemical constituents. This is one of the most important concepts in aromatherapy:
CONCENTRATION CHANGES EVERYTHING. WHY QUALITY MATTERS
Many factors can influence the chemistry of an essential oil:
• botanical species and chemotype
• genetics
• soil
• climate
• rainfall
• sunlight
• altitude
• cultivation practices
• harvesting
• processing
• extraction method
• distillation
• storage
The same species grown in different environments can produce oils with different chemical profiles. This is why responsible sourcing matters.
ADULTERATION
Is there evidence that the oil has been diluted, altered, or adulterated? Don’t assume that an expensive bottle is automatically better. Don’t assume that beautiful packaging equals quality. And don’t assume that every inexpensive oil is poor quality.
Learn how to evaluate your supplier.
RESPONSIBLE AROMATHERAPY BEGINS LONG BEFORE YOU OPEN THE BOTTLE. IT BEGINS IN THE FIELD.
ESSENTIAL OIL CHEMISTRY
Essential oils contain complex mixtures of chemical constituents. These molecules are responsible for much of an oil’s:
• aroma
• volatility
• stability
• physiological activity
• irritation potential
• sensitization potential
• phototoxicity
• therapeutic considerations
The chemistry also helps explain why two oils can smell very different and behave very differently—even when they come from plants with similar characteristics.
A SIMPLIFIED CHEMISTRY GUIDE
MONOTERPENES
General character: Bright, fresh, highly volatile.
Examples: Lemon, orange, rosemary.
Primary consideration: Oxidation.
SESQUITERPENES
General character: Deeper, heavier, less volatile.
Examples: Cedarwood, ginger, spikenard.
Primary consideration: Individual chemistry and stability.
MONOTERPENOLS
General character: Often balancing and relatively gentle.
Examples: Lavender, tea tree, neroli.
Primary consideration: Individual oil matters.
SESQUITERPENOLS
General character: Deeper, grounding, restorative.
Examples: Patchouli, sandalwood, vetiver.
Primary consideration: Individual chemistry matters.
ESTERS
General character: Soft, floral, sweet, relaxing.
Examples: Lavender, clary sage, chamomile.
Primary consideration: Individual oil matters.
PHENOLS
General character: Hot, stimulating, antimicrobial.
Examples: Clove, oregano, cinnamon.
Primary consideration: Skin irritation.
ALDEHYDES
General character: Fresh, lemony, intense.
Examples: Lemongrass, Melissa.
Primary consideration: Irritation potential.
KETONES
General character: Variable and oil-specific.
Examples: Rosemary, peppermint.
Primary consideration: Some require additional caution.
OXIDES
General character: Fresh, penetrating.
Examples: Eucalyptus, rosemary.
Primary consideration: Mucous-membrane irritation.
This chart is a starting point—not a substitute for studying the individual oil. A chemical family does not have one universal effect. The complete chemical profile matters. Rather than trying to memorize every constituent, begin learning to ask:
WHAT DOES THIS OIL CONTAIN, AND HOW DOES THAT CHEMISTRY INFLUENCE THE WAY I USE IT?
LAVENDER
Lavender is a wonderful example because it contains significant amounts of constituents such as linalool and linalyl acetate. Its chemistry contributes to its characteristic aroma and many of the properties for which lavender is traditionally valued.
PEPPERMINT
Peppermint contains a significant amount of menthol and other constituents that contribute to its characteristic cooling sensory experience. Its aroma can feel bright, penetrating, and stimulating. Again, sensory experience and safety considerations need to be considered together.
EUCALYPTUS
Eucalyptus oils can contain significant amounts of 1,8-cineole. This oxide contributes to the characteristic fresh, penetrating aroma associated with many eucalyptus oils. Because strong aromatic exposure can irritate sensitive individuals, method and concentration matter.
CLOVE
Clove contains a high proportion of eugenol, a phenolic constituent. This contributes to its strong, warm, spicy aroma and antimicrobial activity—but also means that clove requires particular care with topical dilution.
THE OLFACTORY PATHWAY
One of the most fascinating aspects of aromatherapy is the relationship between scent and the brain. When we inhale aromatic molecules, they interact with receptors within the olfactory system. Signals travel through the olfactory pathway to the olfactory bulb and onward to areas of the brain involved in emotion, memory, motivation, and nervous system regulation. This helps explain why a smell can instantly transport us to another time or place. A particular perfume can remind us of a person. The smell of a particular plant can bring back a childhood memory. A familiar aroma can create an immediate sense of comfort or recognition. This is part of what makes aromatherapy so powerful as a sensory practice. We aren’t simply smelling something pleasant. We are engaging one of the body’s most direct sensory pathways.
ESSENTIAL OILS & THE SKIN
Essential oils are highly concentrated.
For topical use, I always recommend diluting essential oils rather than routinely applying them neat to the skin. The appropriate concentration depends on:
• the essential oil
• the chemical constituents
• the purpose of use
• the application site
• the individual’s age and circumstances
• skin condition
• frequency of use
• duration of exposure
CARRIER OILS
Carrier oils help disperse essential oils across the skin and reduce their concentration.
Examples include:
• jojoba
• sunflower
• olive
• sweet almond
• apricot kernel
• fractionated coconut
Jojoba is technically a liquid wax ester rather than a conventional vegetable oil. Its composition is similar to components of our skin’s natural sebum, making it a great option for many skincare applications.
SAFETY ESSENTIALS
Essential oils can have real physiological effects. That is exactly why we need to respect them. Some essential oils or their constituents can:
• irritate the skin
• cause sensitization
• cause phototoxic reactions
• irritate mucous membranes
• interact with medications
• be inappropriate for certain individuals
• become problematic with excessive or prolonged exposure
More is not better.
A few drops can represent a significant concentration of aromatic compounds. When using essential oils topically, consider the purpose of the preparation and choose an appropriate dilution. The goal is not to use the strongest possible preparation. The goal is to use the appropriate concentration for the intended application.
PHOTOTOXICITY
Some expressed citrus oils contain naturally occurring compounds called furanocoumarins. These compounds can increase photosensitivity. When certain phototoxic oils are applied to the skin and followed by exposure to ultraviolet light, a phototoxic reaction may occur.
Possible reactions include:
• redness
• burning
• blistering
• pigmentation changes
Particular caution is warranted with some expressed citrus oils, including certain preparations of:
• bergamot
• lime
• lemon
The extraction method matters. Not every citrus essential oil has the same phototoxicity profile. Always check the specific oil and follow current safety guidance.
OXIDATION
Essential oils can change over time. Exposure to:
• oxygen
• heat
• light
• time
can alter their chemistry. Oxidized oils may have increased potential for skin sensitization.
Store essential oils:
• tightly closed
• away from excessive heat
• protected from direct light
• appropriately labeled
• with attention to age and condition
PREGNANCY & BREASTFEEDING
Pregnancy and breastfeeding require additional consideration.
Some essential oils may be appropriate in certain circumstances, while others may not be. Concentration, method of application, individual circumstances, and the specific oil all matter. If you are pregnant, trying to conceive, or breastfeeding, consult a qualified healthcare provider and/or appropriately trained aromatherapy professional before using essential oils therapeutically.
INTERNAL USE
I do not recommend casual internal use of essential oils.
Putting essential oil in water does not dilute it evenly. Oil and water do not mix. Internal use creates a different type of exposure and introduces additional concerns involving:
• toxicity
• irritation
• dosing
• interactions
• individual health circumstances
Some practitioners study internal aromatherapy in specialized clinical settings. That is a different level of education and practice from the foundational aromatherapy we are discussing today. For most applications, inhalation and appropriately formulated topical use provide meaningful ways to work with essential oils without ingesting them.
THE ART OF BLENDING
Once we understand the foundation, we can begin creating intentional blends. Blending is not simply putting several beautiful smells together. A good blend considers:
CHEMISTRY: What constituents are present?
AROMA: How do the oils smell individually and together?
PURPOSE: What experience or application are we trying to create?
SAFETY: Is the oil appropriate for this person and method of use?
SEASON: Does the botanical character fit the season or environment?
PLANT CHARACTER: What part of the plant are we working with?
PERSONAL ASSOCIATION: What does the aroma evoke for the individual?
INTUITION: What does your sensory experience tell you?
KEEP YOUR BLENDS SIMPLE: When you’re learning to formulate, resist the temptation to use ten or fifteen essential oils in one blend.
Start with: 2–5 OILS.
Give every ingredient a reason to be there.
Ask: Why did I choose this oil?
What does it contribute?
How does it smell with the other oils?
What does its chemistry tell me?
Is it safe at this concentration?
Does it support the purpose of the blend?
A good blend is not necessarily the blend with the most ingredients. SIMPLICITY ALLOWS YOU TO UNDERSTAND WHAT YOU ARE CREATING.
THE CHARACTER OF THE PLANT
There is another way to approach blending that I particularly enjoy. We can consider the part of the plant from which the aromatic material comes. This is a symbolic and intuitive approach—not a substitute for chemistry or safety assessment. It gives us another way to develop a relationship with the plant.
SEEDS
Potential · Creativity · New Beginnings. Seeds contain the potential for future growth.
Symbolically, seed botanicals can represent:
• creativity
• potential
• nourishment
• new beginnings
• reproductive vitality
• movement
Examples:
Nutmeg
Black Pepper
Carrot Seed
Fennel
Dill
ROOTS
Grounding · Stability · Nourishment. Roots anchor the plant to the earth.
They can symbolically represent:
• stability
• security
• nourishment
• grounding
• connection to the earth
Examples:
Ginger
Turmeric
WOOD & TRUNK
Structure · Strength · Resilience. The trunk provides structure and stability.
Wood botanicals can symbolically represent:
• strength
• resilience
• centeredness
• direction
• internal stability
Examples:
Cedarwood
Sandalwood
Juniper
Birch
Rosewood
LEAVES, TWIGS & NEEDLES
Breath · Communication · Exchange. Leaves interact with light, air, and water.
They can symbolically represent:
• breath
• communication
• expression
• adaptability
• exchange
Examples:
Fir
Spruce
Eucalyptus
Pine
Rosemary
FLOWERS
Love · Beauty · Relationship. Flowers invite pollination, attraction, connection, and reproduction.
They can symbolically represent:
• love
• friendship
• beauty
• creativity
• emotional connection
• nurturing
Examples:
Rose
Jasmine
Ylang-Ylang
German Chamomile
FRUIT
Nourishment · Joy · Inspiration. Fruit protects and nourishes the seed.
Fruit-derived aromas can symbolically represent:
• joy
• nourishment
• creativity
• inspiration
• refreshment
• lightness
Examples:
Orange
Lemon
Grapefruit
Mandarin
RESINS
Protection · Restoration · Reverence. Resins are part of the tree’s natural protective response.
Historically, resins have been used in:
• incense
• meditation
• ritual
• ceremony
• sacred space
Symbolically, they can represent:
• protection
• healing
• reflection
• restoration
• reverence
Examples:
Frankincense
Myrrh
ESSENTIAL AROMATHERAPY PRINCIPLES
As you continue exploring aromatherapy, remember:
Essential oils are concentrated botanical materials.
Natural does not automatically mean safe.
Concentration matters.
Chemistry matters.
Quality and sourcing matter.
The method of application matters.
The individual matters.
More is not better.
Keep your blends intentional and simple.
Know why you chose every ingredient.
WORKING WITH RESPECT
Essential oils are fascinating because they allow us to encounter plants from several different perspectives.
We can approach them through:
CHEMISTRY
Understanding the molecules that make up the oil.
AROMA
Experiencing fragrance, texture, intensity, and balance.
PHYSIOLOGY
Considering how constituents may interact with the body.
SENSORY EXPERIENCE
Observing how scent influences mood, memory, and perception.
PLANT CHARACTER
Considering the botanical story and part of the plant being used.
INTUITION
Developing a personal sensory relationship with the plants.
The goal is not simply to memorize which oil “does what.”
The deeper practice is learning how to:
LISTEN. OBSERVE. UNDERSTAND. WORK RESPONSIBLY.
When we understand the chemistry, respect the safety considerations, and develop a relationship with the plants themselves, blending becomes more than simply combining beautiful scents. It becomes an intentional botanical practice.
THERE IS NO SINGLE PERFECT BLEND.
There is only the blend that is appropriate for the person, the purpose, the moment—and the plants you have chosen to work with.
TAKE THIS WITH YOU
KNOW THE PLANT.
KNOW THE CHEMISTRY.
KNOW THE CONCENTRATION.
KNOW THE PERSON.
KNOW THE APPLICATION.
BLEND INTENTIONALLY.
AND ALWAYS WORK WITH RESPECT.
PRIMROSE APOTHECARY
Botanical Beauty · Aromatherapy · Education · Plant Wisdom
