Answer:

Scented candles and essential oils are popular for relaxation, improving ambiance, or repelling insects. However, concerns about their impact on respiratory health are common.

Generally, burning scented candles or diffusing essential oils does not directly cause respiratory illness in most healthy individuals. Yet, frequent use in enclosed or poorly ventilated spaces can increase indoor fine particulate matter and pollutant concentrations, potentially affecting respiratory health, particularly in sensitive individuals.

The U.S. Environmental Protection Agency (EPA) identifies burning candles as an indoor source of fine particulate matter, alongside cooking, smoking, and fireplace use. During combustion, candles release PM2.5, soot, volatile organic compounds (VOCs), and other incomplete combustion products. Emission levels vary based on wax composition, fragrance, wick quality, usage duration, and room ventilation.

Some scented candles, especially those made from paraffin wax, can emit VOCs like benzene and formaldehyde. The World Health Organization (WHO) classifies these as indoor air pollutants affecting health. Formaldehyde exposure, specifically, can irritate the eyes, nose, and upper respiratory tract.

Using essential oil diffusers in enclosed spaces for extended periods can irritate the respiratory tract. Illustration. Duong Anh

Essential oil diffusers also impact indoor air quality. Many essential oils contain terpenes – natural scent compounds from plants – which emit VOCs when diffused. When terpenes react with ozone in the air, they can form ultrafine particles and secondary pollutants.

Regular inhalation of VOCs or exposure to fine particulate matter can adversely affect the respiratory system. These tiny dust particles penetrate deep into the alveoli, causing irritation to the eyes, nose, and throat. They can also worsen symptoms of bronchial asthma and chronic obstructive pulmonary disease (COPD). Children, the elderly, and individuals with heart-lung conditions are most susceptible.

For those with bronchial asthma, allergic rhinitis, or chronic respiratory conditions, strong scents from candles, essential oils, or synthetic fragrances can irritate airway mucous membranes. This can trigger coughing, sneezing, nasal congestion, shortness of breath, or asthma attacks. Even individuals without allergies may experience headaches, stinging eyes, or discomfort from prolonged exposure to strong fragrances.

To mitigate risks, use scented candles and essential oils sparingly, choose products from reputable sources, and ensure adequate ventilation during use.

Dr. Nguyen Van Ngan

Department of Respiratory Medicine

Tam Anh General Hospital Hanoi