In general, candles are not considered toxic if they are made with quality materials and burned safely. However, some types of candles can be potentially toxic, especially if they are made with synthetic waxes or poor quality fragrances. When a candle burns, it can release harmful substances into the air, such as hydrocarbons, volatile organic compounds (VOCs), fine particles and aldehydes. VOCs and fine particles can irritate the respiratory tract and contribute to indoor air pollution. Aldehydes can be toxic to health if inhaled in high enough quantities. To minimize potential health risks, it is important to choose candles made with quality materials, such as beeswax or soy wax, and to avoid candles scented with synthetic fragrances. It is also important to burn candles safely, following safety guidelines such as placing them away from combustible materials and extinguishing them when unattended.