Clove, lemon, cinnamon, eucalyptus and rosemary -- this combination has gained the reputation of being a cure-all because of the legend of 4 robbers who stole from sick and dying people during the plague in the 1400s. It's believed that the men used a combination of these spices/herbs to stay healthy.
I can easily see how drinking tisanes (herbal tea) made from these ingredients or using these herbs/spices in their food could have boosted their immune systems. (They didn't have essential oils back then, but the herbs/spices contain minute quantities of essential oils, so they would have ingested minuscule amounts.)
Fast forward to present time and we see thousands of people using this combination of essential oils for just about everything under the sun. It's so popular, that just about all of the big EO companies have their own version. With that in mind, let's look at the therapeutic properties and at the precautions that should be taken when using the oils in this blend.
Clove Essential Oil is comprised of about 85% Eugenol and 8% β-caryophyllene. Therapeutically, Clove is a super oil - it's strongly antimicrobial (kills germs - bacterial, fungal, viral), analgesic (relieves pain), anti-inflammatory (reduces swelling), and anticoagulant (inhibits blood clotting). It's main chemical constituent, Eugenol, is a member of the Phenol chemical family. In small amounts and for short periods of time, Eugenol can be highly effective in supporting health, however, too much and/or for too long can have the opposite effect and become harmful. This is because phenols are chemicals that are very powerful. They are also reactive (they release a hydrogen atom and bind with protein molecules of the skin). This reactive property is damaging to the skin. As a result, it's recommended to use Eugenol at low dilutions - 1% or less - for short periods of time and always with a skin healing/nourishing carrier oil. People with sensitive skin should keep total phenol dilution to 0.5% or less. So the cautions for Clove oil include: dilute to 1% or less with a carrier oil, do not use on damaged or irritated skin or mucous membranes, do not use if you have a blood clotting disorder or are taking blood thinners, Use for short periods of time.
Lemon Essential Oil is about 66% limonene and 12% β-pinene. These chemicals belong to the monoterpene chemical family. Limonene supports the immune system by activating white blood cells. Monoterpenes tend to be antiseptic, decongestant, anti-inflammatory, and skin penetration enhancers. In this case, Lemon Essential Oil is analgesic, antibacterial, antiviral, antispasmodic, and cooling. The caution with this oil is that it needs to be diluted to less than 2% due to phototoxicity. (Using this oil at higher dilutions will cause a skin reaction if UV exposure occurs within 12 - 18 hours of application.) If oxidized, it will cause skin irritation or sensitization.
Cinnamon Essential Oil contains 65% cinnamaldehyde -- which belongs to the aldehyde chemical family -- and 2% eugenol (which we've discussed above). Cinnamaldehyde is anti-inflammatory, antibacterial, antioxidant, and antifungal. As an aldehyde, it is likely to sensitize and irritate the skin. If the dilution is too high, it can harm the liver and the kidneys. The maximum dilution for application to the skin is 0.05%. Cinnamon EO is a great oil to use for short periods of time and in very small quantities -- a maximum of 1 drop per 40 mL (1 1/3 oz) of carrier oil. Do not use this oil if you are pregnant, breastfeeding, or with children under the age of 5.
Eucalyptus Essential Oil comes in a variety of species, all of which are rich in a chemical called 1,8 Cineole which is a member of the Oxide chemical family. This chemical is highly antimicrobial and has mucolytic and expectorant properties. It also has an anti-inflammatory effect in the lungs. Most of us are familiar with the power of Eucalyptus to open our airways quickly. There are some cautions that come with using Eucalyptus EO: Do not use on or near children under the age of 10 as it can slow their central nervous system and/or breathing; use with caution if you have asthma - it could help open the airways or it could set off an asthma attack.
Rosemary Essential Oil has a mix of chemical families in its composition with the highest being monoterpenes, ketones, and oxides. The main constituents are
α-pinene, camphor, camphene, and 1,8-cineole. We've talked about the monoterpenes and oxides in some of the other oils, so we'll focus on the ketone - camphor - as we discuss this oil. Ketones make great expectorants and mucolytics - they clear out the respiratory tract. They are also great at fighting respiratory infections. They need to be used in small amounts over short periods of time because they can accumulate in the liver since they are not easily metabolized. Camphor, in particular, is antibacterial, analgesic, antitussive, and mucolytic. Camphor also has several safety concerns: Do not use on or near the faces of infants - it can cause respiratory collapse; May cause convulsions from ingestion, and rarely, from inhalation; Too much may cause depression of the Central Nervous System; Maximum skin application should be kept to 4.8 % or less. Rosemary Essential Oil has analgesic, antimicrobial, and anti-inflammatory properties. It's wonderful for clearing germs out of the air as well. It's important to keep in mind that it is contraindicated for people with epilepsy or a seizure disorder, if pregnant, and for children under the age of 5. Be very careful if using with children ages 5 - 10 (and monitor breathing).
Looking at the oils used and their primary chemical constituents, we see a substantially antimicrobial blend - I can understand why the 4 robbers didn't catch the plague with these herbs/spices in their pockets. We also see essential oils that need to be used in low dilutions, with skin nourishing/healing carrier oils, and for short periods of time - no more than 3 - 5 days. A blend containing these oils should not be used with children under the age of 10, with women who are pregnant or breastfeeding, or with anyone who has a seizure or blood clotting disorder or is taking blood thinners.
As a trained and certified aromatherapist, I analyze my own blends to a much greater extent than I have done with this. Here, I've done a brief analysis of just the primary chemicals, and I see significant amounts of phenols, ketones, aldehydes, and oxides - four chemical families that can be very effective, and very hard on the human body. Frankly, this is not an essential oil blend I would make or use personally. What scares me about it is that I've heard that people actually ingest blends like this and/or use them without dilution. I shudder to think how much damage they are doing internally and to their skin - damage that may not become immediately apparent, but may show up much later -- when it's too late to reverse. On the other hand, making this with the actual spices/herbs brewed as a tisane, would be delicious and provide the therapeutic benefits without the risk!
Post Script: Check out Robert Tisserand's Blog on the topic of proper dilution. You can find it here. https://tisserandinstitute.org/new-survey-reveals-dangers-of-not-diluting-essential-oils/