How to Apply Essential Oils

如何使用精油

How to Use Essential Oils

(File:Bottles of essential oils and perfume.jpg - Wikimedia Commons) Essential oils are concentrated aromatic compounds extracted from various parts of plants such as flowers, leaves, stems, roots, or fruits, and they are highly volatile (Essential oil - Wikipedia). Due to their strong scents, essential oils are widely used in perfumes, flavorings, cosmetics, and are the core materials of aromatherapy (Essential oil - Wikipedia). Essential oils are typically extracted via steam distillation, though methods like mechanical pressing, solvent extraction, resin tapping, or cold pressing are also used in certain cases (Essential oil - Wikipedia). Despite being called "oils," essential oils are not traditional fats or oils; their main components are volatile organic compounds like terpenes. Common single essential oils include lavender, tea tree, peppermint, eucalyptus, lemon, rose, chamomile, and ylang-ylang. Different essential oils vary in aroma and effects depending on their plant source.

Basic Introduction to Essential Oils

Definition and Source: Essential oils generally refer to volatile aromatic molecules extracted from specific parts of aromatic plants, which are secondary metabolites of the plant. Essential oil glands can be found in plant petals, leaves, bark, rhizomes, and even fruit peels, from which the concentrated aromatic liquid essence can be extracted through appropriate methods (Essential oil - Wikipedia). These substances are volatile at room temperature and insoluble in water, hence the name essential "oil." However, essential oils do not contain fatty oil components but are primarily composed of various terpene compounds. Within the plant, essential oils help regulate growth, defend against pathogens and pests, etc.; in human applications, the aromatic properties of essential oils are used for mood enhancement and health and wellness purposes.

Common Types: There are hundreds of single essential oils available on the market, each with unique aromas and effects. For example, Lavender essential oil has a fresh, gentle scent and is known for relaxation and aiding sleep; Tea Tree essential oil has a camphoraceous odor and is often used for acne treatment and skin disinfection due to its strong antimicrobial properties; Peppermint essential oil is rich in menthol, emitting a cool, pungent aroma that can refresh the mind and alleviate headaches; Eucalyptus essential oil has a refreshing scent with camphoraceous notes and is often used to clear airways and relieve coughs (These three essential oils are respiratory tract cleaners, keep them at home! - Zhihu Column); Citrus essential oils like Lemon and Sweet Orange have bright fruity scents that can uplift mood; Rose essential oil, known as the "Queen of Essential Oils," is prized in beauty for its moisturizing and antioxidant properties (Skincare Special -- Plant Essential Oils Delay Skin Aging - Zhihu Column); Chamomile essential oil has a soft, sweet aroma with soothing, calming, and anti-inflammatory effects, suitable for relieving skin sensitivity. These are just some of the common essential oils; the chemical composition and mechanism of action vary for each, requiring selection based on specific needs.

Extraction Methods: Extracting essential oils requires techniques that can release the aromatic molecules from the plant. The most traditional and common method is steam distillation: plant material is boiled with water, and the steam carries the volatile aromatic components out, which are then condensed and separated to yield the essential oil (Essential oil - Wikipedia). Oils like lavender, peppermint, tea tree, patchouli, and eucalyptus are often obtained this way. For certain oil-rich fruit peels (like lemon, sweet orange), mechanical pressing is commonly used to directly squeeze out the oil (Essential oil - Wikipedia). The aromatic compounds from delicate flowers (like jasmine, tuberose) can be preserved through solvent extraction or the traditional enfleurage method. Modern industry has also developed new techniques like supercritical carbon dioxide extraction, which efficiently extracts heat-sensitive aromatic substances at low temperatures. Different methods have their pros and cons, but all aim to preserve the plant's aromatic components to the greatest extent possible.

How to Use Essential Oils

Essential oils have diverse uses, primarily categorized into three main methods: olfactory inhalation, topical application to the skin, and internal consumption under specific conditions. Different methods affect the pathway into the body and the speed at which effects manifest.

Aromatic Inhalation (Aromatherapy)

(File:Candle Diffuser.jpg - Wikimedia Commons) Aromatic inhalation involves breathing in the volatile scent of essential oils through the respiratory tract to exert physiological or psychological effects. This can be done using various tools to disperse the oil into the air, such as using a diffuser (aroma diffuser) to atomize the oil, burning an aromatherapy candle where the oil volatilizes with the heat, or applying drops to an aroma patch/essential oil necklace for slow release. In home environments, electric water-based diffusers or candle diffusers are often used to heat a container of water and essential oil, filling the room with aromatic mist. Inhalation can be indirect (like diffusing scent in a room) or direct (placing 1 drop of oil on a tissue and sniffing it under the nose). Via the olfactory pathway, essential oil molecules stimulate olfactory receptors in the nasal mucosa, sending signals to the brain's limbic system, thus influencing emotions, memory, and other psychological activities. They can also enter the bloodstream via the lungs to exert effects on bodily functions. Aromatic inhalation is fast-acting and one of the simplest and most common ways to use essential oils. For example, diffusing lavender essential oil in the bedroom before sleep helps create a relaxing atmosphere conducive to sleep; inhaling the scent of sweet orange or bergamot oil during times of stress can alleviate anxiety.

Topical Use (Skin Application)

Applying essential oils topically to the skin is another primary route of use, including methods like massage, bathing, compresses, and spot application. Due to their high concentration and potency, pure essential oils usually should not be applied directly to large areas of skin (Essential oil - Wikipedia). For topical use, essential oils must first be diluted in a suitable ratio with a base oil (also known as a carrier oil) to reduce irritation and promote absorption (Essential oil - Wikipedia). Common carrier oils include sweet almond oil, grapeseed oil, and jojoba oil, which are non-irritating and moisturizing, helping the essential oil penetrate the skin. When blending, typically add 1-3 drops of essential oil to 5 ml of carrier oil (about 1%-3% concentration) for use on the face or other delicate skin; body massage can use a higher concentration, but generally not exceeding 5%. Massage is one of the most common topical methods, using massage movements to enhance oil penetration and boost local blood circulation. For instance, massaging sore muscles with diluted rosemary or ginger essential oil can help relieve tension and pain. Bathing is also popular: add essential oils to warm bathwater (usually 5-10 drops, mixed first with bath salts or milk to disperse), allowing absorption through both skin and respiration for relaxation and skin care. Additionally, blended essential oil massage oils can be used for spot application/compresses, such as dabbing a diluted peppermint oil blend on the temples to relieve headaches, or applying a gel containing tea tree oil to pimples for anti-inflammatory and antibacterial effects. Because essential oil molecules are very small and lipid-soluble, they can quickly penetrate the skin and enter the bloodstream and lymphatic system. Topically absorbed essential oils are metabolized and completely eliminated from the body without long-term residue.

Internal Use (Use with Caution)

Internal use of essential oils refers to ingesting essential oils orally, aiming for certain therapeutic or health benefits. However, it must be emphasized that casual internal consumption of essential oils is not recommended unless under the guidance of a qualified professional aromatherapist or physician. Ingesting undiluted pure essential oils directly is strictly forbidden as it can cause burns to the mouth and esophagus, or lead to severe adverse effects like liver and kidney toxicity. Certain essential oils (like lemon, peppermint) are used internally in capsule form within the European Aromamedicine system to assist in treating issues like indigestion or respiratory infections, but these applications must be determined by qualified professionals based on specific conditions and individual circumstances. Generally, if oral intake is necessary, the essential oil must first be diluted in a medium such as honey, vegetable oil, or milk before consuming a small amount. Even so, the choice of oil and dosage is critical and requires professional guidance: for example, the English school of aromatherapy generally does not advocate oral use, while the French school of aromatic medicine employs oral therapy in specific clinical situations. Therefore, internal use of essential oils is reserved for special circumstances and should be avoided for non-urgent or non-professional needs. Anyone considering ingesting essential oils should consult a doctor or certified aromatherapist to ensure safety and efficacy.

Essential Oil Recommendations for Different Needs

Different types of essential oils have unique characteristics and are often used to meet specific needs related to physical and mental well-being. Below are recommendations for selecting and using essential oils for common needs such as relaxation and sleep, anxiety relief, headache and muscle pain reduction, skin care, and respiratory improvement.

Relaxation and Sleep Aid

Relaxing the body and mind and improving sleep quality are among the most well-known benefits of aromatherapy. Research suggests that the aroma of certain essential oils can act on the autonomic nervous system, helping to lower stress hormone levels and relax muscles, thereby promoting sleep. Lavender essential oil is the most famous for this—high-quality lavender oil has calming and sedative effects; its floral scent can ease tension, reduce sleep latency, and improve sleep quality. Placing 1 drop of lavender oil on a pillow or diffusing it before bed can help induce sleep with its sweet floral aroma. Besides lavender, Roman Chamomile essential oil, containing ethers, also helps soothe emotions and dispel irritability, beneficial for insomnia; the rich earthy and floral scents of Vetiver essential oil and Ylang Ylang essential oil are often used for deep relaxation and meditation, contributing to deeper sleep. Among citrus oils, the fresh fruity scent of Bergamot essential oil has also been shown to have calming effects, suitable for relieving anxiety-induced insomnia. Some studies indicate that blending multiple essential oils may be more effective in improving sleep quality than using a single oil. Commercial sleep aid blends often feature lavender combined with oils like sweet marjoram or ylang-ylang for synergistic effects. A simple way to use oils for sleep is to add a few drops of lavender or ylang-ylang oil to a warm bath before bed, relaxing the body and inhaling the aroma to prepare for sleep. Personal preference and reaction to scents are important; choose an aroma that feels soothing to you.

Relieving Anxiety and Stress

Aromatic molecules from essential oils can influence the limbic system via the olfactory nerve, thereby regulating emotions and alleviating psychological stress. During times of anxiety or high mental pressure, the right essential oil aroma can have a calming effect on emotions and soothe the nerves. True Lavender essential oil has been repeatedly shown to be highly effective in reducing anxiety; its scent promotes the release of calming neurotransmitters in the brain, inducing relaxation. Studies suggest components like esters and sesquiterpene lactones found in oils such as lavender and chamomile can act on the central nervous system, reducing sympathetic nerve activity and thus alleviating anxiety symptoms. Sweet Orange essential oil and Bergamot essential oil are known for mood elevation; these fresh, sweet fruity scents reduce stress without causing excessive sedation, making them suitable for daytime use to dispel tension and fatigue. In clinical aromatherapy, neroli oil, derived from bitter orange blossoms (also known as Neroli essential oil), rich in nerol, is considered particularly effective against panic and for calming nerves, often used to relieve anxiety and improve depressive moods. Besides single oils, several relaxing essential oils can be blended in appropriate ratios. For example, **"Anti-Stress Blends"** often use lavender as a base, adding ylang-ylang, sweet orange, or sandalwood for a more comprehensive soothing effect. When using such oils, inhalation offers the quickest results: apply a drop to a tissue and inhale deeply several times, or carry a personal inhaler. Diffusing the oil in an office or bedroom can also create a sustained calming atmosphere, helping maintain a peaceful state of mind.

Relieving Headaches and Muscle Soreness

Essential oils are often used as natural pain relievers and soothing agents, offering help for common discomforts like headaches and muscle soreness. For tension headaches (e.g., head pressure pain caused by stress or fatigue), Peppermint essential oil, containing menthol, is a common choice. Mix 1-2 drops of peppermint oil with a small amount of carrier oil and gently massage onto the temples and forehead; the cooling sensation gradually relieves head tightness after a few minutes. Reports suggest that topical application of a 10% peppermint oil solution in alcohol can be comparable to conventional painkillers in relieving tension headaches. Peppermint's stimulating aroma can also provide a mental lift, dispelling the fatigue often associated with headaches. Lavender essential oil also possesses analgesic properties; its gentle calming effect is suitable for relieving migraines and stress-related headaches—inhaling lavender aroma in a quiet environment or massaging the forehead and neck with diluted lavender oil can help reduce headache discomfort. For muscle soreness and joint stiffness, essential oil massage can relax muscles and promote circulation. Wintergreen essential oil (derived from the Gaultheria plant) contains natural methyl salicylate, offering anti-inflammatory and analgesic effects similar to aspirin, often used to soothe post-exercise muscle aches and joint pain. However, wintergreen oil should be used cautiously, as high concentrations or large-area application can be toxic. Safer options include Sweet Marjoram essential oil and Basil essential oil; the former warms muscles and relieves spasms, while the latter has relaxing effects. Both are often used in massage for sore muscle groups. Additionally, Ginger essential oil and Black Pepper essential oil have warming effects; adding a small amount to massage oil can promote local blood circulation and relax tense muscles. In practice, blend the chosen essential oil(s) at a 2%-3% concentration in a carrier oil to create a massage oil, rub into sore areas for 5-10 minutes to help soothe pain and reduce inflammation. Adding a few drops of rosemary, eucalyptus, or ginger oils to a hot bath can also alleviate muscle soreness and fatigue. When using essential oils for pain relief, be mindful of individual differences; some people may be sensitive to stimulating oils like peppermint. Start with a low dose and observe the reaction.

Skin Care

Many essential oils are widely used in skin care due to their antibacterial, anti-inflammatory, and cell-regenerating properties, addressing issues like acne, dryness, and signs of aging.

• Acne-Prone Skin Care: For skin troubled by acne such as pimples and blackheads, Tea Tree essential oil is one of the most well-known natural remedies. Tea Tree oil (from the leaves of Melaleuca alternifolia) is rich in active components like terpinen-4-ol, possessing broad-spectrum antibacterial and antifungal properties that effectively inhibit the growth of Propionibacterium acnes, the bacteria causing acne. Clinical studies show that using a gel containing 5% tea tree oil significantly reduces skin inflammation, helping alleviate mild to moderate acne. Compared to conventional anti-acne treatments like benzoyl peroxide, tea tree oil may work slightly slower but has fewer side effects, such as excessive drying. To use, apply 1 drop of tea tree oil directly onto pimples with a cotton swab, or add a few drops to your daily lotion for spot treatment. Note that tea tree oil should not be used over large areas for extended periods, as it might cause skin irritation or dryness.
• Moisturizing Dry and Sensitive Skin: Some essential oils can improve skin dryness and strengthen the skin barrier function. For instance, Rose essential oil and Lavender essential oil are often added to skincare products for their soothing and moisturizing benefits (Extraction of plant essential oils and their application in cosmetics - Industry News - Daily Chemicals - CIRS Group). The various alcohols and phenolic compounds in rose oil possess antioxidant activity, neutralizing free radicals and reducing environmental damage to the skin (Skincare Special -- Plant Essential Oils Delay Skin Aging - Zhihu Column). The aroma of rose also promotes relaxation, offering relief for stress-related dryness (e.g., dull skin from late nights or mental tension). Lavender essential oil is known for promoting cell regeneration and anti-inflammatory effects, useful for soothing sunburnt skin, dryness, flakiness, and minor skin irritations. Adding a few drops of lavender oil to a carrier oil for facial massage provides both moisturizing and relaxing benefits. Furthermore, Frankincense essential oil (from frankincense resin) has been traditionally used in the Middle East for skincare; its resin alcohols are thought to help diminish fine lines and scars. Carrot Seed essential oil, rich in carotenes and pro-vitamin A, helps moisturize the skin and improve complexion, suitable for dry, dull skin types. For sensitive skin prone to allergies, gentle oils with anti-inflammatory properties like Chamomile or Lavender are safer choices. However, even with gentle oils, a skin patch test should be performed before first use to ensure no allergic reaction occurs.
• Anti-Aging Care: As skin ages, signs like fine lines, sagging, and age spots appear. Some essential oils are considered natural aids in anti-aging due to their antioxidant and cell-conditioning properties (Extraction of plant essential oils and their application in cosmetics - Industry News - Daily Chemicals - CIRS Group). For example, the aforementioned Rose essential oil, rich in potent antioxidants like citronellol and geraniol, can scavenge excess free radicals and promote collagen synthesis, earning it the title "Queen of Essential Oils" and widespread use in anti-wrinkle and firming skincare products (Skincare Special -- Plant Essential Oils Delay Skin Aging - Zhihu Column). Sandalwood essential oil, with its soft woody scent and anti-inflammatory properties, can help improve aging caused by inflammation, leading to smoother, more even skin texture. Ylang Ylang essential oil, besides balancing oil secretion, may also help tone sagging skin associated with menopause. It's important to note that the anti-aging effects of essential oils are mostly supplementary. Their mechanisms mainly involve: utilizing antioxidant activity to combat free radical damage, partial UV absorption by some oils to reduce photoaging, and the moisturizing effect slowing down dryness-related aging (Extraction of plant essential oils and their application in cosmetics - Industry News - Daily Chemicals - CIRS Group). Therefore, consider adding small amounts of essential oil to face creams or serums in daily skincare to enhance antioxidant and moisturizing effects. However, essential oils cannot compare to medical anti-aging treatments and cannot reverse deep wrinkles. Their function is similar to plant extract skincare—focused on long-term conditioning and prevention. Remember to avoid fragile areas like around the eyes, use low concentrations, and be mindful of sun protection (some oils are photosensitive, see below). Discontinue use if irritation or intolerance occurs.

Improving Respiratory System Issues

In respiratory health care, the aromas of certain essential oils are believed to have air-purifying and respiratory symptom-relieving effects. For example, Eucalyptus essential oil, due to its main component eucalyptol (1,8-cineole) having expectorant and antibacterial properties, holds a place in traditional remedies for colds and coughs (These three essential oils are respiratory tract cleaners, keep them at home! - Zhihu Column). Eucalyptus oil can help relax bronchial smooth muscles and promote mucus expulsion, thus alleviating nasal congestion and breathing difficulties. Adding 2-3 drops of eucalyptus oil to a bowl of hot water for steam inhalation, or blending it with peppermint oil for a chest rub, are common folk methods for relieving cold-related nasal congestion (These three essential oils are respiratory tract cleaners, keep them at home! - Zhihu Column) (Teaching you how to use essential oil massage to treat colds and fevers_body temperature - Sohu). Similarly, Peppermint essential oil, with its cooling menthol, stimulates cold receptors in the nasal mucosa, creating a sensation of clear breathing (Respiratory System Aromatherapy Applications—Four Secrets to Explore Spring Health - Aromatherapy Academy). When experiencing nasal congestion or a sore throat, adding a few drops of peppermint oil to hot water for steam inhalation can help open airways with its cooling steam, relieving congestion caused by colds or allergies (Respiratory System Aromatherapy Applications—Four Secrets to Explore Spring Health - Aromatherapy Academy). Peppermint's refreshing effect can also combat the lethargy associated with colds (Respiratory System Aromatherapy Applications—Four Secrets to Explore Spring Health - Aromatherapy Academy). Besides eucalyptus and peppermint, Tea Tree essential oil and Thyme essential oil, known for their antibacterial and antiviral properties, are often used to purify indoor air and prevent respiratory infections—for example, adding a small amount to a humidifier tank allows the oil to disperse with the mist, potentially reducing airborne pathogens and allergens (Discussion on the efficacy of respiratory care essential oil formulas in clinical applications). Commercially available "respiratory relief" blends often contain ingredients like Pine Needle, Fir Needle, Peppermint, Camphor, aiming to comprehensively alleviate discomfort in the throat and nasal passages. For chronic conditions like bronchitis or asthma, some respiratory support formulas might use Frankincense essential oil (from frankincense resin) and Myrrh essential oil, which are claimed to reduce airway inflammation and stabilize emotions, aiding in long-term management. However, it must be stressed that essential oils cannot replace medical therapy. For serious conditions like asthma, follow medical advice for medication; essential oils can only serve as supplementary soothing aids. When using essential oils for respiratory issues, apply them in low concentrations to the throat, neck, and chest (avoiding the area under the nose to prevent strong irritation), or use diffusion methods for slow, continuous release in a room. Ensure adequate ventilation to prevent overly concentrated odors from causing discomfort.

Precautions and Safety Tips for Using Essential Oils

Although essential oils are natural products, improper use can still lead to side effects and safety risks. To safely and effectively enjoy the benefits of essential oils, pay attention to the following precautions:

• Dilution Concentration: Never apply high-concentration essential oils directly to large areas of skin. Most essential oils need to be diluted with a vegetable carrier oil to a low concentration before skin contact. Generally, body massage oils should have an essential oil concentration of 2%-5%, while sensitive areas like the face should use <2%. Direct application of concentrated essential oils can cause burning, redness, or irritation (Essential oil - Wikipedia). If spot application of potent oils (like tea tree, clove) is needed, limit it to a small affected area and control the amount and frequency.
• Skin Patch Test: Before using a new essential oil for the first time, perform a skin patch test for allergies. Apply a small amount of the diluted essential oil to a tender skin area, like the inner forearm, and wait 24 hours to observe for redness, itching, rash, or other adverse reactions (Essential oil - Wikipedia). If any abnormality occurs, it indicates a possible allergy or intolerance to that oil, and its use should be discontinued. Individuals with allergies or sensitive skin should be especially cautious and always test new oils. Avoid contact with eyes and mucous membranes. If accidental eye contact or irritation occurs, rinse immediately with plenty of water and seek medical attention (Essential oil - Wikipedia).
• Children, Pregnant Women, and Pets: Use of essential oils on children and infants requires extreme caution. Infants have delicate skin and immature metabolic systems, so stimulating essential oils are generally not recommended for children under 2. Older children may use very low concentrations of gentle oils like lavender or chamomile under professional guidance, avoiding ingestion. Pregnant women should avoid oils that might stimulate the uterus or have potential toxicity, such as rosemary, clary sage, fennel, and juniper, which are generally considered contraindicated during pregnancy, especially the first trimester, unless advised otherwise by a doctor. During pregnancy, milder oils like lavender and citrus can be used sparingly and at very low concentrations for stress relief or insomnia, preferably via inhalation rather than massage. Pets have lower tolerance to essential oils, and many oils safe for humans can be toxic to cats and dogs. For example, cats lack the liver enzymes to metabolize certain essential oil components (like phenols, terpenes), and inhalation or ingestion can cause vomiting, drooling, ataxia, and, in severe cases, liver damage or respiratory failure. Oils like tea tree, wintergreen, camphor, clove, cinnamon, citrus, peppermint, and eucalyptus are particularly toxic to cats and dogs and should be strictly avoided for pet use or diffusion in enclosed spaces with pets. Even with relatively safer scents like lavender, ensure good ventilation when pets are present and allow them the freedom to leave the area. If a pet has a pre-existing respiratory condition, do not use essential oil products in its living space.
• Photosensitive Oils: Some essential oils contain photosensitive (phototoxic) compounds that can cause pigmentation or burns when applied to the skin and exposed to sunlight (UV radiation). Typical examples are citrus essential oils like bergamot, lemon, lime, and bitter orange obtained by cold pressing, which contain furanocoumarins. After using such oils (especially topically), avoid direct sun exposure on the treated skin for at least 12 hours or longer (Essential oil - Wikipedia). For example, if you use a body massage oil containing lemon essential oil in the morning, take care to use sunscreen or cover the application area with clothing when going outdoors during the day to prevent sunspots or burns. Comparatively, distilled citrus oils labeled as FCF (Furanocoumarin-Free) are much safer as the photosensitive components have been removed. When unsure if an oil is photosensitive, it's prudent to use it at night or ensure thorough sun protection.
• Quality and Storage: The quality of essential oils directly impacts safety. Choose pure, natural essential oils from reputable brands and avoid low-quality synthetic fragrances masquerading as essential oils, as impurities can be harmful (Essential oil - Wikipedia). High-quality essential oils usually indicate the Latin name, origin, and extraction part, often supported by purity test reports. Essential oils are volatile and sensitive to heat and light. Store them sealed in dark glass bottles in a cool, dark place. Once opened, essential oils should ideally be used within 1-2 years (citrus oils have a shorter shelf life, about 6 months after opening), as prolonged exposure to air causes oxidation and degradation, potentially increasing skin irritation. Ensure the bottle cap is tightly screwed after each use to minimize evaporation and oxidation. Keep essential oil bottles out of reach of children to prevent accidental ingestion or spills. Adhere to the principle of moderation when using essential oils; more is not always better. Follow recommended dosages and avoid overuse or excessively frequent application.

In summary, essential oils, as natural healing resources, can bring physical and mental pleasure and health benefits when used appropriately, but safety must be the priority. Beginners should consult authoritative aromatherapy resources or seek guidance from professional aromatherapists, starting with low doses and single oils to understand their effects on their body and mind. If any adverse symptoms (like headache, nausea, rash) occur during use, stop immediately and consult a medical or aromatherapy professional (Essential oil - Wikipedia). By treating essential oils scientifically and prudently, we can fully enjoy the gifts of nature's fragrances, enhancing our quality of life while ensuring our safety.

References:

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2. Wikipedia: Aromatherapy
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4. Xiamen University Cardiovascular Hospital:科普 (Popular Science) on Aromatherapy and Anxiety
5. Mayo Clinic: Clinical effects of Tea Tree Oil (Tea tree oil - Mayo Clinic)
6. CIRS Cosmetics Regulation: Application of Essential Oils in Skin Care (Extraction of plant essential oils and their application in cosmetics - Industry News - Daily Chemicals - CIRS Group) (Extraction of plant essential oils and their application in cosmetics - Industry News - Daily Chemicals - CIRS Group)
7. Jandan.net: Potential toxicity of essential oils to pets
8. Wikipedia: Essential oil safety guidelines (Essential oil - Wikipedia)