Palo Santo, or Bursera graveolens, is an aromatic wood sourced from a tree native to the dry tropical forests of South America, particularly in Ecuador and Peru. Translating to “holy wood” in Spanish, this fragrant material has been used for centuries in traditional purification rituals and folk medicine practices. Beyond its spiritual and therapeutic applications, a widespread belief suggests that the smoke and scent of Palo Santo can effectively repel insects. This claim, often passed down through generations, raises the question of whether this aromatic wood holds genuine scientific merit as a natural insect deterrent.
The Chemistry Behind the Scent
The distinctive, sweet, and slightly citrus aroma of Palo Santo results from a complex blend of volatile organic compounds (VOCs) concentrated in the wood and its essential oil. The primary component is a monoterpene called limonene, which can constitute up to 44% to 50% of the essential oil’s composition. Limonene is a compound well-known in the field of pest control and is found in many commercial natural insecticides. This terpene acts as a deterrent and an insecticide by interfering with the nervous systems of various insects. Other significant aromatic compounds present include alpha-terpineol (around 17%) and phellandrene (up to 24%). These compounds contribute to the wood’s potent scent profile and its theoretical repellent qualities.
Scientific Evidence of Efficacy
The theoretical potential of Palo Santo as a repellent is high because of its rich limonene content, yet controlled studies specifically on its efficacy against common pests like the Aedes aegypti mosquito are limited. Many claims of effectiveness remain largely anecdotal, rooted in the long history of traditional use rather than modern laboratory trials. The scientific community often requires data on the specific concentration and duration of a repellent’s effect to validate a natural remedy.
Existing research on the Bursera genus and similar essential oils does confirm a strong insecticidal activity against various species. For example, studies have demonstrated that Palo Santo essential oil is effective against stored-product pests, such as the bean weevil (Acanthoscelides obtectus), showing a high level of repellency, sometimes reaching nearly 90%. This evidence suggests that the wood’s compounds are chemically capable of acting as insect deterrents, but the successful results are specific to certain insect types and application methods.
For mosquitoes, the most common target of concern, the primary mechanism of action is likely the smoke and strong scent creating a physical barrier rather than a toxic effect at a distance. While the chemical components are promising, there is a lack of published data confirming the concentration of burning Palo Santo smoke needed to repel mosquitoes for a measurable duration compared to commercial repellents.
Safe Use as an Insect Deterrent
When using Palo Santo as a repellent, the most common method involves lighting a stick of the wood until a stream of fragrant smoke is produced, which is then used to treat an outdoor area. The essential oil form offers an alternative application, which can be diffused or diluted with a carrier oil before being applied topically to the skin.
Since the burning wood produces smoke, it is important to ensure adequate ventilation to prevent potential respiratory irritation. Inhaling any type of smoke can be irritating to the respiratory system, particularly for individuals with pre-existing conditions like asthma or allergies. Direct inhalation of the thick smoke should be avoided, and the wood should only be burned in open or well-ventilated spaces. When using the essential oil on the skin, it must always be mixed with a neutral carrier oil to prevent contact dermatitis or other skin sensitivities. Caution should be exercised when using either the smoke or the essential oil around infants, young children, or pregnant individuals.