This article originally appeared in the NAHA Journal (Spring 2019) and it is republished here according to the NAHA Writer Guidelines 2019-20 copyright statement.
By Kathy Sadowski, MS in Aromatherapy, RA (ARC), Professional NAHA and AIA Member, LMT
The plants commonly called oregano (Origanum vulgare), sweet marjoram (Origanum marjorana), and thyme (Thymus vulgaris) have a confusing combination
of similarities and differences. For example, there are thyme species with marjoram common names (Thymus mastichina is commonly called Spanish
marjoram). Further, marjoram is part of the Origanum (oregano) genus and there are an astonishing variety of chemotypes. With that
being said, the most important information to research when identifying a
bottle of essential oil from one of these species is its chemistry profile.
Why is the chemistry so important?
Here are some examples.
is a marjoram species (O. majorana ct.
carvacrol) whose chemistry is more like that of the oregano species (O. vulgare) because it is high in the
chemical component of carvacrol.
species (T. vulgaris ct. linalool) is
very similar to the linalool chemotype of wild marjoram ( O. majorana ct. linalool).
arethyme plants (T. vulgaris ct. thymol) that are high in
carvacrol and thymol, similar to oregano (O.
cannot automatically assume oregano (O.
vulgare) and thyme (T. vulgaris)
essential oils are “hot” while marjoram (O.
marjorana) essential oil is more gentle. These chemo-varieties
come with vastly different therapeutic uses, therapeutic margins, and
This article will first provide an overview of the
plant varieties. Then, it will discuss the importance of knowing the major chemical
constituents for a specific essential oil as well as therapeutic uses and
contraindications associated with the chemistry of the oil.
Overview of Plant Varieties
Below is a general overview of oregano, sweet marjoram,
and thyme. It is important to know the many variations of these plants.
Oregano (Origanum vulgare) is
a perennial herb growing up to thirty inches tall, with opposite spade-shaped
leaves about one inch long. Its flower are tiny purple spikes. Dried aerial
parts are used to make the essential oil, which is mostly made up of carvacrol,
with thymol, and monoterpenes. The aroma is very strongly herbal and not
typically used in perfumery.
marjorana) is a perennial herb like oregano, with oval-shaped
soft hairy leaves about a half inch long. Flowers are tiny white or pink spikes.
Dried areal parts are used to make the essential oil. The aroma of this essential
oil is camphoraceous, woody, and spicy.
Thyme (Thymus vulgaris) is
a bushy evergreen shrub growing up to one foot tall. Its leaves are smaller
than oregano and sweet marjoram, with a grey-green color, and tiny pale pink or
purple flowers. Arial parts are used to make the essential oil. The essential oil
is often rectified, with vast species variations as well. Two key chemotypes of
this essential oil are Thymus vulgaris ct.thymol, with a medicinal and herbal aroma, and Thymus vulgaris ct. geraniol, with a sweet and herbal aroma.
In the plant family, Lamiaceae there are over 200 genus, and over 7,000 species. Oregano
and sweet marjoram are of the Origanum genera, and thyme is of the Thymus genera.
There are over fifty plant species in the Origanum genus, including sweet marjoram
(O. marjorana) and oregano (O. vulgare).
Sweet Marjoram (Origanum marjorana) hasmultiple species with very different chemotypes.
marjoram (O. majorana) is typically high in monoterpenes, alcohols, and
esters. It has about 30% terpinen-4-ol, plus sabinene, linalyl acetate,
terpinenes, cymene, and a small amount of linalool.1
Another “sweet” French type of O. marjorana has over 50% 1,8-cineole,
up to 12% linalool, with terpenes.2
Wild marjoram (O. majorana ct.carvacrol) has a type
that is very high in carvacrol, with up to 81%.1
Wild marjoram (O. majorana ct. linalool) also has type that is very high in linalool (upwards of
66%), and also has a high amount of carvacrol.1
A Spanish chemotype (O. majorana ct.1,8-cineole)
can contain over 62% 1,8-cineole.2
Oregano hasmultiple species, subspecies, and
chemotypes, which are characteristically very high in carvacrol. Species include: O. onites, O, vulgare, and O. syriacum.
There are over 350 plant species in the Thymus genus, including the most
familiar Thymus vulgaris, whichhas multiple chemotypes.
Thymus vulgaris Chemotypes:
T. vulgaris ct. geraniol, which may commonly be
called sweet thyme, can contain up to 80% geranyl acetate and geraniol.2
T. vulgaris ct. limonene contains mostly thymol,
limonene, and carvacrol.1
T. vulgaris ct. linalool can contain up to 79%
linalool, with a high amount of linalyl acetate.1
T. vulgaris ct. carvacrol is high in carvacrol.1
T. vulgaris ct. thymol, also called red thyme, is
high in thymol.1,2
Other Thymus Species:
mastichina has the confusing common name of Spanish marjoram,
even though it is not in the Origanum genus. Its chemistry is about 50% 1,8-cineole, with camphor, alpha pinene,
camphene, borneol, beta pinene, and alpha-terpineol.
satureioides is high in borneol, carvacrol, beta
terpineol, and thymol.
Commonly called lemon thyme, Thymus citriodorus is high in geraniol,
with carvacrol, geranial, neral, and other components.
Species high in carvacrol and thymol include: T. spicata (spike thyme), T. zygis (often called Spanish thyme), and T. serpyllum, also known as creeping
After reviewing the chemistry associated with the
varieties of oregano, sweet marjoram, and thyme, we see certain chemical
constituents repeatedly. Here are three key points to consider when looking at
the constituents of these three plant essential oils.
with a strong therapeutic activity, but a small therapeutic margin, include: Phenols
(carvacrol and thymol), ketones including camphor, and the oxide 1,8-cineole. Essential oils high in these constituents
should be avoided with pregnant women, small children, and those with certain medical
Monoterpenes are light in molecular weight
and include: Terpinene, limonene, cymene, sabinene, and pinene. These constituents
are analgesic, anti-inflammatory, anti-spasmodic, and antimicrobial. Being
highly volatile, these constituents are most prone to oxidation; oxidized oils can
cause skin irritation.3
constituents with a calming, anti-inflammatory, analgesic, anti-spasmodic, and antimicrobial
effect include alcohols and esters such as: Linalool, terpinen-4-ol, borneol,
geraniol, and geranyl acetate. These less chemically reactive constituents are
generally safer to use with most people.3
Carvacrol and Thymol
Phenols are very reactive chemical constituents, and
thus have a small therapeutic margin, with potential toxicity in excess or when
used for prolonged periods. Essential oils high in phenolic constituents should
be avoided during pregnancy, with small children, and only used topically in
very high dilution ratios. Small amounts can cause skin and mucus membrane
irritation. These constituents may also be contra-indicated with multiple
medical conditions and may interact with certain medicines.3
Essential oils high in carvacrol and thymol are potent
antimicrobials, antioxidants, insecticidal, and have a stimulating effect:
is an essential oil constituent identified as having one of the strongest
Thymol has also demonstrated
antimicrobial activity in multiple studies.5
and carvacrol are two of the strongest antioxidant constituents of 423 tested
has shown insecticidal and repelling action in multiple scientific studies.7
has a small therapeutic margin, that could be toxic in excess. Prolonged usage
should also be avoided. It is not appropriate for children, those who are pregnant,
and those with certain medical conditions. On the flip side, camphor has
demonstrated antimicrobial action in multiple studies, and may help with
respiratory complaints and pain:
In one human study, participants with the common cold who
inhaled a mixture of aromatic vapors of eucalyptus, menthol, camphor, experienced
Another human study
showed a topical cream containing
glucosamine sulfate, chondroitin sulfate, and camphor reduced symptoms of
arthritis in the knee.9
constituent1,8-cineole can be organ
and neurotoxic in excess. It can also be a respiratory irritant. It is not
appropriate to use with small children, those who are pregnant, and people with
certain medical conditions, such as asthma.
of 1,8-cineole are its antimicrobial, insecticidal, anti-inflammatory, and
demonstrated good expectorant activity in a study of 386 patients with
respiratory disease in an emergency room.10
Cineole may be effective as an anti-inﬂammatory
and analgesic agent based on an
in vivo study showing reduced rat paw inflammation and pain reactions.11
Cineole, citral, geraniol, linalool and menthol were
tested against a variety of bacteria and fungi, showing a range of
Limonene, Cymene, Sabinene, and Pinene
can be antimicrobial, analgesic, and anti-spasmodic. Being highly volatile,
these constituents are most prone to oxidation. Oxidized monoterpene rich
essential oils can cause skin irritation.3
Alcohols and Esters:
Linalool, Terpinen-4-ol, Borneol, Geraniol, and Geranyl Acetate
tend to have a low toxicity rating compared to other chemical constituents and
are safer with children and those in fragile health. Esters are similar to
alcohols, with a gentle nature, and form when an acid combines with an alcohol.
Alcohols and esters tend to have analgesic, anti-spasmodic, anti-inflammatory,
and antimicrobial activities. They are
associated with a calming effect, such as with linalool.13
What Should I do?
Based on all these
chemistry variations, the best thing to do when purchasing and/or using a
bottle of sweet marjoram, oregano, or thyme essential oil, is to first review a
GC-MS (Gas chromatography–mass
This should be accessible from reputable essential oil companies. It is a report that lists the amounts of each
chemical constituent found in a batch of essential oil. This
helps you to understand the unique chemistry profile of the specific bottle of
essential oil you are buying. A trained nose may also be able to distinguish some
key aroma constituents in an essential oil.
Herbal Stuffy Nose Tea
fresh oregano leaves, or 1/4 tsp of dried oregano (Origanum ssp.)
tsp. of honey
oz. of hot water
for Making and Use:
hot water over the oregano leaves. Then, allow them to steep for ten minutes.
strain the leaves. Finally, add honey, and drink as a tea.
Adult Use Only. Do not exceed one cup a day. Furthermore, do
not drink for a prolonged period exceeding two weeks. Avoid use with small
children, with pregnant women, and with certain medical conditions. It may increase bleeding in those with bleeding
disorders. Avoid up to two weeks before surgery. It might lower blood sugar levels and affect
medications related to diabetes.
Oil Bug Spray Recipe
tsp. of dish soap
witch hazel (Hamamelis virginiana) or
tsp. of sea salt
drops of sweet marjoram (Origanum majorana) OR
thyme (Thymus ssp.)
drops of Texas cedarwood (Juniperus
mexicana) OR juniper berry (Juniperus
communis)20 drops of blue gum eucalyptus (Eucalyptus globulus) OR citronella (Cymbopogon nardus)
for Making and Use:
mix the dish soap, essential oils, and witch hazel or vodka together in an 8 oz.
spray bottle. Separately, bring the water and salt to a boil and then simmer
until the salt dissolves. Add the cooled salt water to the bottle; shake
Adult Use Only. Shake the bottle and
spray an amount equal to
about 1 tsp onto the skin. Re-apply
as needed, and shake the bottle before each use. Avoid eyes and mucous
membranes. Discontinue use if irritation occurs Not for prolonged use. Avoid use in pregnancy,
with young children, and with certain medical conditions.
Tisserand, R. & Young, R. (2014).
Essential Oil Safety, 2nd Edition. Churchill Livingstone, Elsevier.
Lis-Balchin, M. (2006). Aromatherapy
Science. A Guide for Healthcare
Professionals. Pharmaceutical Press.
(2003). The Chemistry of Aromatherapeutic
Oils, 3rd Edition. Allen
Can Baser, K. H. (2008). Biological and
pharmacological activities of carvacrol and carvacrol bearing essential oils. Current
pharmaceutical design, 14(29), 3106-3119.
Solórzano-Santos, F., & Miranda-Novales,
M. G. (2012). Essential oils from aromatic herbs as antimicrobial agents.
Current opinion in biotechnology, 23(2), 136-141.
Anthony, K. P., Deolu‐Sobogun, S. A., &
Saleh, M. A. (2012). Comprehensive assessment of antioxidant activity of
essential oils. Journal of food science, 77(8), C839-C843.
Nerio, L. S., Olivero-Verbel, J., &
Stashenko, E. (2010). Repellent activity of essential oils: a review.
Bioresource technology, 101(1), 372-378.
Cohen, B. M., & Dressier, W. E. (1982).
Acute aromatics inhalation modifies the airways. Effects of the common cold.
Respiration, 43(4), 285-293.
Cohen, M., Wolfe, R., Mai, T., & Lewis, D.
(2003). A randomized, double blind, placebo controlled trial of a topical cream
containing glucosamine sulfate, chondroitin sulfate, and camphor for
osteoarthritis of the knee. The Journal of rheumatology, 30(3),
Li, G. A. O. (1989). The expectorant effect of
cineole compositus in 386 patients with respiratory diseases. Chinese
Journal of Rehabilitation;1995-03.
Santos, F. A., & Rao, V. S. N. (2000).
Anti-inflammatory and antinociceptive effects of 1, 8-cineole a terpenoid oxide
present in many plant essential oils. Phytotherapy research, 14(4),
Pattnaik, S., Subramanyam, V. R., Bapaji, M.,
& Kole, C. R. (1996). Antibacterial and antifungal activity of aromatic
constituents of essential oils. Microbios, 89(358), 39-46.
Linck, V. M., Da Silva, A. L., Figueiró, M.,
Caramão, E. B., Moreno, P. R. H., & Elisabetsky, E. (2010). Effects of
inhaled Linalool in anxiety, social interaction and aggressive behavior in
mice. Phytomedicine, 17(8), 679-683.