Citronella is a widely used natural product, extracted as an essential oil from Cymbopogon grasses, primarily Cymbopogon nardus (Ceylon type) and Cymbopogon winterianus (Java type). This aromatic oil is known globally for its distinctive citrus scent and its use as an effective insect repellent and fragrance agent. While low-level application in candles, sprays, and diffusers is generally considered safe, concentrated citronella oil poses a significant toxicological risk. Improper handling, especially ingestion of the concentrated form, can lead to severe adverse health effects. The potential for harm is directly related to the oil’s concentration and the route of exposure.
Understanding Citronella’s Chemical Structure
Citronella oil is a complex essential oil composed of naturally occurring monoterpenoid compounds that give it its characteristic properties. The oil’s potency and specific scent profile depend on the source plant, which determines the concentration of its active chemicals. The three main components are citronellal, geraniol, and citronellol, which are responsible for both the insect-repelling action and the potential for irritation.
The Java type (C. winterianus) is often preferred in commerce because it contains a higher percentage of active molecules, typically 32–45% citronellal, 21–24% geraniol, and 11–15% citronellol. This makes it more potent than the Ceylon type. These high concentrations mean the pure, undiluted oil must be handled with care, as its chemical structure makes it a skin and mucous membrane irritant. The chemical makeup dictates the oil’s volatility and its ability to penetrate the skin or mucous membranes.
Toxicity Based on Exposure Pathways
The toxicity profile of citronella oil changes depending on how it enters the human body. Ingestion of concentrated citronella oil presents the most severe risk and is not approved for internal consumption. Swallowing the oil can irritate the digestive tract, leading to gastrointestinal distress. In larger volumes, it carries the danger of central nervous system (CNS) depression. A major concern with ingestion is aspiration, where the oily substance enters the lungs, potentially causing chemical pneumonitis or pulmonary edema.
Dermal, or skin, contact is the most common route of exposure through products like lotions and insect sprays. Undiluted citronella oil is a known irritant that can cause contact dermatitis, a localized skin reaction. The risk of developing irritation or allergic sensitization increases with the oil’s concentration and frequency of application. Repeated or prolonged exposure to high concentrations can lead to cumulative toxicity, resulting in effects like erythema and edema.
Inhalation exposure typically occurs through diffusers or burning candles, which releases the oil’s components in low concentrations. In well-ventilated spaces, this is considered a low risk, as the oil is highly volatile and quickly disperses. However, using high concentrations in enclosed areas can cause respiratory discomfort. Sensitive individuals, such as those with asthma or other respiratory conditions, may experience throat irritation, coughing, or headaches from the concentrated vapors.
Recognizing Signs of Overexposure
Recognizing the signs of overexposure is important for prompt action, as symptoms vary depending on the exposure pathway. Following ingestion, immediate symptoms include nausea, vomiting, and abdominal pain due to irritation of the gastrointestinal lining. More severe signs of systemic toxicity may manifest as drowsiness, dizziness, or uncoordinated movement, indicating CNS effects. If aspiration into the lungs occurs, symptoms like severe coughing, difficulty breathing, or wheezing may develop.
Dermal Overexposure Symptoms
Dermal overexposure is noticeable as a localized skin reaction that can range from mild to moderate. Observable signs include:
- A burning sensation.
- Redness (erythema).
- Persistent itching.
- Rash, hives, or blistering (in cases of significant irritation or allergic reaction).
If a severe skin reaction or any sign of respiratory distress is observed, immediate medical attention is necessary.
First Aid Measures
For any suspected ingestion, contact a poison control center or emergency services. Do not attempt to induce vomiting, as this increases the risk of aspiration into the lungs.
- If the oil contacts the skin, the area should be thoroughly washed with soap and plenty of water to remove the irritant.
- For inhalation exposure, move the person to an area with fresh air to allow the respiratory system to clear.
Safe Handling and Application Guidelines
Safe use of citronella oil centers on proper dilution and storage to minimize the risk of accidental overexposure. For topical application, pure essential oil must always be diluted in a carrier oil. A generally accepted dilution for adult use is between 1% and 2.5% (approximately 6 to 15 drops per ounce of carrier oil). Children and individuals with sensitive skin should use a lower concentration, typically 0.5% to 1%.
The oil should never be applied undiluted directly to the skin, and contact with sensitive areas like the eyes, inner ears, or mucous membranes must be avoided. When using citronella candles or diffusers indoors, adequate ventilation is necessary to prevent the buildup of vapors that could irritate the respiratory tract. Concentrated citronella essential oil should be stored securely and out of the reach of children and pets to prevent accidental ingestion.