The Wonder of Wintergreen
When we think of wintergreen, we probably think of that refreshing minty taste in chewing gum or toothpaste. Or perhaps that icy-hot sensation we feel from applying medicated cream for sore muscles after an intense workout. The essential oil that we call wintergreen is most commonly extracted from the leaves of Eastern Teaberry (Gaultheria procumbens). The oil has a soft pale-yellow to pink color and the plant has been used for hundreds of years in traditional medicine as a pain reliever and fever-reducer.1 Wintergreen is an important essential oil in clinical aromatherapy.
The oil is comprised almost entirely of methyl salicylate.2 Methyl salicylate is widespread amongst deep-heating creams for sore muscles and joints, found in products like Ben-Gay®, Icy Hot®, Tiger Balm®, and Chinese medicine liniments. Most over-the-counter creams contain approximately 30% methyl salicylate, though some can be as high as 70%.3
Pharmacology & Toxicity
Although well-known for its therapeutic effects, wintergreen is not without its hazards. The potent molecule, methyl salicylate, is structurally similar to aspirin (acetyl salicylic acid). After ingestion, methyl salicylate is readily metabolized by the body to salicylic acid, which is the same bioactive intermediate as aspirin. This means that wintergreen essential oil’s mode of action on the body from this compound is identical to its conventional medication counterpart. Therefore, just as aspirin can be toxic, so too can wintergreen essential oil.
Effectively, 1 drop of wintergreen essential oil = ~81 mg of aspirin [a baby aspirin].
Methyl salicylate, similar to aspirin, is absorbed rapidly from the gastrointestinal tract. Research indicates it can take as little as 15 minutes following ingestion to identify traceable amounts in the blood, with a peak around 2 hours following ingestion.4 For aspirin, toxicity has been documented at oral doses around 150 mg/kg (for a 150-lb adult, this is about 32 tablets of 325 mg aspirin or about 1.5 teaspoons of wintergreen essential oil), with serious risk of toxicity at 300-500 mg/kg (for a 150-lb adult, this is about 64 tablets of 325 mg aspirin or about 3 teaspoons of wintergreen essential oil).2,5
In children less than 6 years of age, as little as 4 mL (less than a teaspoon) ingested wintergreen oil has been implicated in several documented deaths.5 It is best to keep essential oil bottles far from the reach of children.
Naturally, oral dosing has the greatest capability for absorption and potential for toxicity; however, topical applications are not without their risks. In 2007, a 17-year old cross-country runner died from the excessive and long-term applications of topical muscle creams for pain relief. The medical examiner’s discovered that there were abnormally elevated levels of methyl salicylate in her body and was the cause of death.6 Due to its chemical nature, methyl salicylate is readily-absorbed by dermal application and is another reason its topical use is concerning.
An overdose of either salicylate leads to a condition called ‘salicylism,’ characterized by the symptoms of dizziness, tinnitus, nausea, vomiting, hyperventilation, mental status changes, with the potential of leading to coma or even death.7
Some individuals have an allergy to aspirin or possess a salicylate sensitivity. These individuals are likely to have a reaction to wintergreen essential oil; as such, it should best be avoided in this population altogether.7
Management of Overdose
In the case of overdose, western medicine treatment interventions may include 50-100 g of activated charcoal (orally), sodium bicarbonate (intravenously), and depending on the severity, hemodialysis. Due to the fact that salicylates affect the acid-base homeostasis within the body, it is pertinent to balance electrolytes and pH, as well as maintain adequate hydration.7
A 2013 study supports the oral hygiene benefits of Gaultheria procumbens oil. The study demonstrated the oil’s effects as an anti-biofilm agent for Streptococcus mutans (pathogen responsible for dental caries) and Candida albicans. This research also revealed the antimicrobial effects across a wide-range of pathogens including, Streptococcus mutans, Candida albicans, Streptococcus sanguis, Streptococcus pyogenes, Pseudomonas aeruginosa, and Staphylococcus aureus.1
In 2014, EcoSmart Technologies, Inc. was issued a patent for a pesticidal formulation containing wintergreen oil, as well as rosemary oil.8 This suggests that the uses of wintergreen may be beyond common understanding and research may pave the way for new and additional applications.
Wintergreen essential oil, as with many essential oils, offer incredible therapeutic effects in clinical aromatherapy. However, they are not without their toxicity concerns. When using essential oils, even if it is simply a topical application or an OTC formulation, it is pertinent to be cognizant of safety concerns and the potential side effects of their use.
To learn more about clinical aromatherapy and aromatherapy chemistry, check out our full aromatherapy continuing education course offerings here.