The Wintergreen plant (Gaultheria procumbens) is a small, evergreen shrub native to North America, recognized by its bright red berries and characteristic minty scent. While the leaves and berries have been used for flavoring and in traditional medicine for centuries, the plant is potentially poisonous. The risk depends entirely on the concentration and amount consumed, as the danger comes from a specific chemical compound that becomes highly concentrated during extraction. Modern concentrated products derived from the plant pose a serious, life-threatening toxicity risk if ingested.
The Source of Toxicity: Methyl Salicylate
The chemical agent responsible for wintergreen’s toxicity is methyl salicylate, which gives the plant its distinctive aroma and taste. Methyl salicylate is chemically similar to acetylsalicylic acid (aspirin). When ingested, the body metabolizes methyl salicylate into salicylic acid, the substance that causes the toxic effects. This compound is highly concentrated in the essential oil extracted from the plant’s leaves, often reaching 98% methyl salicylate. One teaspoon of pure wintergreen oil contains the equivalent amount of salicylate as approximately 21 to 28 adult-strength aspirin tablets.
After ingestion, salicylic acid stimulates the respiratory center in the brain, causing rapid breathing (hyperventilation) and resulting in a temporary condition called respiratory alkalosis. The more severe mechanism involves interfering with oxidative phosphorylation, the process central to cellular energy production. This interference prevents cells from producing energy efficiently, leading to a build-up of lactic acid and other organic acids. This quickly results in a dangerous change in the body’s acid-base balance, causing metabolic acidosis and organ damage.
Toxicity Risk Levels in Plant Parts and Oil
The risk of poisoning is directly related to the concentration of methyl salicylate, which varies drastically between the whole plant and its extracted oil. Consuming a few wintergreen berries or chewing a small leaf poses a low, localized risk, often causing only mild gastrointestinal upset, as the concentration in the raw plant material is too low to cause severe systemic poisoning.
In stark contrast, concentrated wintergreen essential oil is one of the most toxic essential oils available and presents an extreme, life-threatening danger if swallowed. The oil is so potent that ingesting as little as 4 to 6 milliliters (less than a single teaspoon) can be fatal to a child. For adults, the lethal dose can be as low as 6 milliliters, though the usual lethal ingestion is around 30 milliliters.
The danger is also present in topical pain-relieving products like liniments or rubs, which can contain high concentrations of methyl salicylate, sometimes up to 30%. Applying these products repeatedly over large areas, or on broken skin, can lead to systemic salicylate toxicity, especially in children.
Recognizing Salicylate Poisoning Symptoms and Emergency Action
Salicylate poisoning symptoms can range from deceptively mild to severe. Early signs typically include severe nausea, persistent vomiting, and tinnitus (a persistent ringing or buzzing sound in the ears). As the poisoning progresses and the body’s acid-base balance shifts, more serious symptoms develop, including rapid breathing (tachypnea) and confusion or altered mental state. In severe cases, the poisoning can lead to metabolic acidosis, seizures, cerebral edema, and ultimately coma. These life-threatening effects can appear within six hours of ingestion, and symptoms may be delayed or mimic other illnesses, which complicates diagnosis.
If any amount of wintergreen essential oil or concentrated methyl salicylate product has been swallowed, call poison control or emergency services immediately. Do not wait for symptoms to appear before seeking professional medical help. Urgent medical intervention is required to correct the severe metabolic imbalance caused by the toxin.
Safe Use and Handling of Wintergreen Products
Despite its high toxicity when concentrated, wintergreen is safely utilized in many commercial and medicinal products. It is commonly used as a flavoring agent in candies, chewing gum, toothpaste, and some pharmaceuticals, where the concentration of methyl salicylate is negligible or synthetic. It is also widely used in topical pain-relieving rubs, where the methyl salicylate is absorbed through the skin for localized relief of muscle and joint pain.
For safe handling, concentrated wintergreen essential oil must be treated as a household poison, similar to strong cleaning chemicals. All bottles of essential oil and topical rubs containing high concentrations of methyl salicylate must be kept securely out of the reach of children and pets, utilizing child-resistant bottles and appropriate labeling. When using the essential oil topically, it must always be diluted with a carrier oil to minimize the risk of skin irritation and systemic absorption.