The potential toxicity of<unk>  is related to its level or grade of purity, and to the toxicity of specific chemical components of the<unk> . Many<unk> s are designed exclusively for their aroma-therapeutic quality; these<unk> s generally should not be applied directly to the skin in their undiluted form. Some can cause severe irritation, provoke an allergic reaction and, over time, prove toxic to the liver. If ingested or rubbed into the skin,<unk> s can be highly poisonous, causing confusion, choking, loss of muscle coordination, difficulty in breathing, pneumonia, seizures, and possibly severe allergic reactions or coma. Some<unk> s, including many of the citrus peel<unk> s, are photosensitizers, increasing vulnerability of the skin to sunlight. Industrial users of<unk> s should consult the safety data sheets to determine the hazards and handling requirements of particular<unk> s. Even certain therapeutic-grade<unk> s can pose potential threats to individuals with epilepsy or pregnant women.<unk>  use in children can pose a danger when misused because of their thin skin and immature livers. This might cause them to be more susceptible to toxic effects than adults. Flammability The flash point of each<unk>  is different. Many of the common<unk> s, such as tea tree, lavender, and citrus<unk> s, are classed as Class 3 Flammable Liquids, as they have a flash point of 50–60 °C. Gynecomastia Estrogenic and antiandrogenic activity have been reported by in vitro study of tea tree<unk>  and lavender<unk> s. Two published sets of case reports suggest that lavender<unk>  may be implicated in some cases of gynecomastia, an abnormal breast tissue growth in prepubescent boys. The European Commission's Scientific Committee on Consumer Safety dismissed the claims against tea tree<unk>  as implausible, but did not comment on lavender<unk> . In 2018, a BBC report on a study stated that tea tree and lavender<unk> s contain eight substances that when tested in tissue culture experiments, increasing the level of estrogen and decreasing the level of testosterone. Some of the substances are found in "at least 65 other<unk> s". The study did not include animal or human testing. Handling Exposure to<unk> s may cause contact dermatitis.<unk> s can be aggressive toward rubbers and plastics, so care must be taken in choosing the correct handling equipment. Glass syringes are often used, but have coarse volumetric graduations. Chemistry syringes are ideal, as they resist<unk> s, are long enough to enter deep vessels, and have fine graduations, facilitating quality control. Unlike traditional pipettes, which have difficulty handling viscous fluids, the chemistry syringe, also known as a positive displacement pipette, has a seal and piston arrangement which slides inside the pipette, wiping the<unk>  off the pipette wall. Ingestion Some<unk> s qualify as GRAS flavoring agents for use in foods, beverages, and confectioneries according to strict good manufacturing practice and flavorist standards. Pharmacopoeia standards for medicinal<unk> s should be heeded. Some<unk> s can be toxic to some domestic animals, cats in particular. The internal use of<unk> s can pose hazards to pregnant women, as some can be abortifacients in dose 0.5–10 mL, and thus should not be used during pregnancy. Pesticide residues There is some concern about pesticide residues in<unk> s, particularly those used therapeutically. For this reason, many practitioners of aromatherapy buy organically produced<unk> s. Not only are pesticides present in trace quantities, but also the<unk> s themselves are used in tiny quantities and usually in high dilutions. Where there is a concern about pesticide residues in food<unk> s, such as mint or orange<unk> s, the proper criterion is not solely whether the material is organically produced, but whether it meets the government standards based on actual analysis of its pesticide content. Pregnancy Some<unk> s may contain impurities and additives that may be harmful to pregnant women. Certain<unk> s are safe to use during pregnancy, but care must be taken when selecting quality and brand. Sensitivity to certain smells may cause pregnant women to have adverse side effects with<unk>  use, such as headache, vertigo, and nausea. Pregnant women often report an abnormal sensitivity to smells and taste, and<unk> s can cause irritation and nausea when ingested. Toxicology The following table lists the or median lethal dose for common<unk> s; this is the dose required to kill half the members of a tested animal population. LD50 is intended as a guideline only, and reported values can vary widely due to differences in tested species and testing conditions. Common Name Oral LD50 Dermal LD50 Notes Neem 14 g/kg >2 g/kg Lemon myrtle 2.43 g/kg 2.25 g/kg Frankincense >5 g/kg >5 g/kg Boswellia carterii Frankincense >2 g/kg >2 g/kg Boswellia sacra Indian frankincense >2 g/kg >2 g/kg Boswellia serrata Ylang-ylang >5 g/kg >5 g/kg Cedarwood >5 g/kg >5 g/kg Roman chamomile >5 g/kg >5 g/kg White camphor >5 g/kg >5 g/kg Cinnamomum camphora, extracted from leaves Yellow camphor 3.73 g/kg >5 g/kg Cinnamomum camphora, extracted from bark Hot<unk>  3.80 g/kg >5 g/kg Cinnamomum camphora,<unk>  extracted from leaves Cassia 2.80 g/kg 0.32 g/kg
Essential oil
Petroleum jelly
Emu oil
Gutter oil
Lavender oil
Tea tree oil
Coal tar
Balsam of Peru