Quick Answer
To burn incense safely and effectively: choose natural varieties without synthetic binders, use a proper heat-safe holder, ensure ventilation with an open window, set a clear intention before lighting, and never leave burning incense unattended. For meditation, sandalwood and frankincense are the most documented for calm focus. For space clearing, white sage or palo santo are traditional and effective. Quality natural incense transforms the atmosphere of any practice space within minutes.
Table of Contents
- The Ancient History of Incense
- Hildegard von Bingen and the Medicinal Power of Aromatic Plants
- Types of Incense: Sticks, Cones, Resin, and Dhoop
- Choosing Quality Natural Incense
- How to Burn Incense Safely and Effectively
- Incense for Specific Spiritual Purposes
- Using Incense in Meditation Practice
- Space Clearing with Incense
- Making Your Own Incense
- Frequently Asked Questions
Key Takeaways
- Natural over synthetic: Pure plant-based incense with no synthetic fragrance oils or chemical binders is safer, more effective, and spiritually more resonant than mass-market varieties.
- Hildegard von Bingen documented aromatic plant medicine in the 12th century, establishing frankincense, lavender, and rosemary as medicinal aromatics with documented physiological effects.
- Ventilation is non-negotiable: Always burn incense with an open window or door to prevent accumulation of combustion particles in enclosed spaces.
- Intention amplifies effect: Setting a clear purpose before lighting incense, whether meditation, cleansing, focus, or prayer, meaningfully changes the quality of the practice.
- Match scent to purpose: Sandalwood and frankincense for meditation, white sage or palo santo for clearing, rose and jasmine for heart work, vetiver and cedar for grounding.
The Ancient History of Incense
Incense is among the oldest ritual technologies in human history. Archaeological evidence from Egyptian temples at Luxor and Karnak documents the use of aromatic resins in ceremony dating to at least 3,000 BCE. The word "incense" derives from the Latin incendere, meaning "to burn," but the practice itself predates the Latin language by millennia.
In ancient Egypt, incense was not merely a pleasant scent but a substance with cosmological significance. The Egyptians burned kyphi, a complex blend of 16 aromatic ingredients including calamus, mastic, juniper berries, raisins, wine, myrrh, and frankincense, in temple ceremonies honoring Ra and Osiris. The smoke was understood as a physical bridge between the human world and the divine, carrying prayers and offerings upward to the gods. Kyphi was also prescribed medicinally for anxiety, insomnia, and respiratory conditions, representing one of the earliest documented integrations of spiritual and physical healing through aromatics.
Frankincense (Boswellia sacra and related species) occupies a central place in the history of sacred scent across cultures. Traded across the Arabian Peninsula, East Africa, and the Mediterranean for over 5,000 years, frankincense was among the most valuable commodities of the ancient world, frequently mentioned in the same breath as gold. The three Magi bringing frankincense and myrrh to the infant Jesus in the Christian nativity narrative reflects the enormous cultural and spiritual significance these resins carried in the ancient Near East. Frankincense was used in Jewish temple rituals (the Ketoret offering), in Greek and Roman religious ceremonies, and across Buddhist and Hindu traditions in Asia.
Frank Dayrell-Reed, in his 1914 historical study of incense in religious traditions, documented the extraordinary continuity of aromatic practice across cultures that had no direct contact: the simultaneous development of resin-burning ceremonies in Egypt, Mesopotamia, the Indus Valley, and Mesoamerica suggests that the human nervous system's response to specific aromatic compounds drives the practice as much as any cultural transmission. This convergent discovery of incense points toward a genuine, cross-cultural recognition of aromatic plants' effects on human consciousness.
In Japan, the practice of Kodo (the Way of Incense) developed during the Heian period (794 to 1185 CE) into a refined art form comparable to the tea ceremony. Kodo practitioners distinguish between dozens of oud (agarwood) varieties by subtle aromatic differences, approaching scent as a meditative practice requiring years of cultivation. The most prized ingredient is Kyara, a specific grade of oud produced by infection of the Aquilaria tree, which can command prices exceeding gold by weight.
Hildegard von Bingen and the Medicinal Power of Aromatic Plants
Hildegard von Bingen (1098 to 1179 CE) was a Benedictine abbess, composer, visionary, and one of the most remarkable intellectual figures of medieval Europe. Her two major medical works, Physica and Causae et Curae, constitute comprehensive systems of herbal and natural medicine that remained influential for centuries after her death. Hildegard's approach to aromatic plants was grounded in her concept of Viriditas, the "greening power" or vital life force she believed permeated all of nature and could be transmitted to humans through the proper use of natural substances.
On frankincense, Hildegard wrote that its smoke "opens the channels of the mind and clarifies thought that is obscured by earthly concerns." She used lavender smoke specifically for headaches and nervous tension, prescribing patients to inhale lavender vapor through a cloth. Her recommendation of rosemary fumigation for chest ailments and respiratory conditions anticipated by centuries the modern aromatherapy research showing rosemary's expectorant and antimicrobial properties.
Hildegard's medicinal framework was deeply spiritual: she did not separate the physical effects of aromatic plants from their spiritual dimensions. In her view, the same vital force that healed the body through scent also elevated the soul toward God. This integration of physical medicine and spiritual practice through aromatic plants represents one of the most sophisticated early articulations of what we now call aromatherapy.
Hildegard's Key Aromatic Prescriptions
- Frankincense: Mental clarity, spiritual elevation, prayer and contemplation.
- Lavender: Headaches, nervous agitation, sleep disturbance.
- Rosemary: Respiratory conditions, mental fatigue, chest congestion.
- Sage: Digestive complaints, purification of the atmosphere.
- Calamus (Sweet Flag): Calming agitated emotions and excessive melancholy.
Modern aromatherapy research has validated many of Hildegard's specific prescriptions. A 2019 study in the Journal of Traditional and Complementary Medicine confirmed frankincense smoke's anxiolytic (anxiety-reducing) effects in animal models, specifically through activation of TRPV3 ion channels. Lavender essential oil is one of the most extensively researched aromatics, with clinical trials demonstrating effects on anxiety, sleep quality, and pain perception. Rosemary's cognitive enhancement effects have been documented in multiple human studies, including a 2012 paper in Therapeutic Advances in Psychopharmacology showing improved memory speed and accuracy with diffused rosemary oil.
Types of Incense: Sticks, Cones, Resin, and Dhoop
Understanding the different forms of incense allows you to select the most appropriate type for each purpose and context. The main distinctions involve the presence or absence of a bamboo core, the use of synthetic versus natural binding agents, and whether the aromatic material is solid or loose.
Incense sticks (also called joss sticks) consist of aromatic materials pressed onto a thin bamboo core with a natural or synthetic binder. They are the most common and beginner-friendly form, burning cleanly and consistently. The bamboo core produces some smoke independent of the aromatic material, which is why the final burn-down of a stick (the last centimetre) sometimes smells different from the rest. High-quality stick incense uses natural binders like Makko powder (from the Tabu-no-ki tree) rather than synthetic adhesives.
Incense cones contain no bamboo core and use a higher concentration of aromatic material compacted into a cone shape. They produce more fragrance intensity and more smoke than equivalent sticks and are well-suited for larger spaces. Their disadvantage is that they require a holder with a slightly recessed cavity or plate to catch the ash, which falls in a compact pile rather than along a stick's length.
Loose resin incense represents the most traditional and, for many practitioners, the most potent form. Resins like frankincense, myrrh, copal, benzoin, and dragon's blood are the dried exudates of specific trees. They are burned on self-igniting charcoal discs in a heat-safe censer. Because resin incense contains no binders or fillers, it releases the full aromatic complexity of the plant material without synthetic alteration. The learning curve is slightly higher (the charcoal preparation takes five to ten minutes), but the quality and purity of the aromatic experience is unmatched by stick or cone formats.
Dhoop sticks are thick, coreless sticks with a higher aromatic material concentration than standard sticks. They produce rich, dense fragrance and burn for 45 to 90 minutes. Indian Dhoop is frequently used in temple settings because it fills large ceremonial spaces effectively. Tibetan incense is typically a Dhoop-style format using juniper, rhododendron, and other Himalayan plants in traditional formulas handed down within Buddhist monastic lineages.
Choosing Your Incense Format by Use Case
- Short meditation (15-30 min): Standard stick or small cone. One stick times your session naturally.
- Longer ritual or ceremony: Dhoop stick, coil incense, or resin on charcoal for extended fragrance.
- Space clearing: Loose sage, palo santo wood, or resin burned on charcoal provides the most effective coverage.
- Bedtime relaxation: A slow-burning stick of lavender or chamomile lit 30 minutes before sleep.
- Portable or travel use: Pre-made sticks in a travel case; skip resin and charcoal setups for travel.
Choosing Quality Natural Incense
The incense market contains a wide range of quality levels, from genuine plant-based aromatics to sticks saturated with synthetic fragrance oils that mimic natural scents at fraction of the cost. The health and experiential differences between these categories are significant enough to warrant learning to distinguish them.
Synthetic fragrance incense typically has a loud, uniform scent that smells identical from the moment of lighting to extinguishing. Natural incense unfolds in layers: top notes (lighter, more volatile aromatics) appear first, followed by heart notes as the burn progresses, with base notes (heavier resins and woods) emerging last. If an incense smells identical throughout its burn and matches a common commercial fragrance like "ocean breeze" or "fresh linen," it almost certainly contains synthetic fragrance compounds.
Natural binders include Makko (Tabu-no-ki bark powder, the Japanese standard for high-quality stick incense), Tragacanth gum, Gum Arabic, and honey. Synthetic binders include diethyl phthalate (DEP) and similar plasticizers, which produce chemical smoke when burned. Indian Agarbatti sticks using charcoal as a binding base have drawn attention in research for elevated benzene and polycyclic aromatic hydrocarbon (PAH) production compared to natural-binder formats.
Country of origin provides useful guidance. Japanese incense (brands like Shoyeido, Nippon Kodo, and Baieido) is consistently high quality, using natural materials and Makko binders per centuries-old craft traditions. Indian incense varies widely: Dhoop-style Indian incense from traditional manufacturers like Satya and HEM uses natural materials, while many lower-cost Indian sticks use charcoal bases and synthetic fragrances. Tibetan incense from established monastery producers (like Tibetan Medical and Astrological Institute formulas) is consistently pure.
How to Burn Incense Safely and Effectively
Burning incense safely requires attention to ventilation, holder selection, fire safety, and sensitive occupants in the space. None of these requirements are complicated, but skipping them creates real risks.
Ventilation: Always ensure at least one window or door is open while burning incense. Even natural incense produces combustion byproducts including carbon monoxide, fine particulates, and volatile organic compounds. In a well-ventilated space, these dissipate rapidly. In a sealed room, they accumulate. The ventilation requirement is especially important for people with asthma, respiratory sensitivities, or cardiovascular conditions.
Holders: Use a holder designed for your incense type. Stick incense requires a holder with a hole for the bamboo end, positioned over an ash-catching tray. Cone incense needs a heat-resistant flat surface or slightly recessed holder. Resin incense requires a metal censer or fireproof bowl filled with sand (to insulate the bowl from charcoal heat). Never balance an incense stick against a surface without a proper holder; falling ash and the risk of the stick rolling are genuine fire hazards.
Step-by-Step: Burning Loose Resin on Charcoal
- Fill a heat-safe censer or bowl with two to three centimetres of sand or salt to insulate from charcoal heat.
- Hold a self-igniting charcoal disc with metal tongs and ignite one edge with a lighter until sparks travel across the disc (30 to 60 seconds).
- Place the lit disc in the prepared bowl and wait two to three minutes for it to fully heat and turn slightly grey at edges.
- Place a small amount of resin (a few granules of frankincense, or a small chip of myrrh) on the glowing disc.
- Allow to burn for one to two minutes, then add more resin as needed. Less is more: a pea-sized amount per addition produces gentle, continuous fragrance without overwhelming smoke.
- Never leave burning charcoal and resin unattended. The charcoal remains hot for up to one hour after the resin has finished.
Sensitive occupants: Incense smoke should not be burned around infants, young children, people with asthma or COPD, cats (particularly sensitive to essential oils and combustion products), birds (extremely sensitive to airborne particles), or pregnant women. If any of these occupants are present, either burn incense in a separate room with the door closed, or use an electric diffuser with essential oils as a smoke-free alternative.
Incense for Specific Spiritual Purposes
Different aromatic plants carry distinct energetic qualities recognized across multiple spiritual traditions. While individual response to scent is personal, certain associations have been maintained across cultures and centuries with enough consistency to constitute a practical guide.
Meditation and contemplation: Sandalwood is the foremost choice across Buddhist, Hindu, and Taoist traditions. Its woody, warm, slightly sweet scent reduces anxiety and promotes calm alertness without drowsiness. Frankincense deepens breathing, quiets the autonomic nervous system, and has a 3,000-year documented history in prayer and contemplative contexts. Nag Champa, a blend of sandalwood and champak (champaca) flower, is closely associated with meditation halls globally and has become one of the most widely recognized spiritual scents in the world.
Space clearing and protection: White sage burns with a strong, herbaceous smoke that Indigenous North American traditions use for purification of persons, objects, and spaces. Palo santo (Bursera graveolens) produces a warmer, sweeter smoke used in South American traditions for clearing while maintaining a protective, welcoming energy. Juniper, used across First Nations traditions of the Pacific Northwest, combines clearing and protective properties. Frankincense is used for sacred space preparation in Catholic, Orthodox, and many esoteric Western traditions.
Heart-centered practices and love work: Rose incense (from real rose otto or absolute, not synthetic rose fragrance) opens the heart chakra and is traditionally associated with Venus energy, love, compassion, and emotional healing. Jasmine carries similar heart-opening qualities with a more intoxicating quality associated with spiritual devotion in Hindu puja practice. Ylang-ylang supports emotional release and sensory awareness.
Grounding and stability: Vetiver is perhaps the most grounding of all aromatic plants, its deep, earthy, smoky scent anchoring scattered energy to the present moment. Patchouli combines earth energy with a slight sweetness. Cedarwood is used across multiple traditions for strength, stability, and protection. Myrrh combines deeply grounding resin with subtle bitter notes associated with wisdom and the completion of cycles.
Scent Associations by Purpose at a Glance
- Meditation and focus: Sandalwood, frankincense, Nag Champa, cedarwood
- Space clearing: White sage, palo santo, juniper, cedar
- Heart work and love: Rose, jasmine, ylang-ylang, sweet orange
- Grounding: Vetiver, myrrh, patchouli, oakmoss
- Energy and vitality: Cinnamon, clove, orange peel, ginger
- Sleep and rest: Lavender, chamomile, Roman chamomile, valerian
Using Incense in Meditation Practice
Incense serves several specific functions in meditation that make it more than atmospheric decoration. First and most practically, it marks time: a standard incense stick burns for 20 to 40 minutes, functioning as a natural timer for meditation sessions without electronic interruption. The end of the stick, signaled by a different quality of smoke or the disappearance of active burning, gently signals the session's close without jarring alarm sounds.
Second, the ritual of lighting incense functions as a threshold marker, a cue that shifts the nervous system from ordinary task mode toward receptive awareness. Neurologically, this works through classical conditioning: when the smell of a specific incense becomes consistently paired with meditation, the nervous system begins the transition to meditative states before the formal sitting even begins. After several weeks of consistent practice, the smell of your meditation incense can trigger a measurable relaxation response before you have taken a single conscious breath.
Third, the act of watching smoke is a traditional concentration object (Dharana practice) in itself. Following the unpredictable curls and dispersals of incense smoke with sustained attention is a genuine mindfulness practice that develops the quality of soft, open attention required for deeper meditation. Many teachers recommend beginning sessions with five minutes of smoke observation before transitioning to breath awareness or mantra.
Establishing an Incense Meditation Ritual
- Select your incense based on the day's meditation intention (see scent guide above).
- Place the incense in its holder and sit quietly for one minute before lighting, setting your intention for the session.
- Light the incense with a single match or lighter. Blow out any flame gently, leaving the glowing tip.
- Watch the first curls of smoke for two to three minutes as a concentration practice, following each tendril with relaxed, non-grasping attention.
- Transition to your primary meditation method (breath, mantra, body scan, or visualization) when attention feels settled.
- When the incense naturally extinguishes, take two to three minutes to close the session before moving into daily activity.
The physiological mechanism by which specific scents affect meditation quality involves the olfactory system's direct connection to the limbic brain. Unlike every other sense, olfactory signals bypass the thalamus and connect directly to the amygdala (the brain's primary emotional processing center) and hippocampus (the seat of memory). This is why certain scents produce immediate emotional responses and memory associations that feel involuntary. In meditation, deliberately using specific scents to invoke states of calm, focus, or heart-openness makes intentional use of this neurological shortcut.
Space Clearing with Incense
Space clearing with aromatic smoke is documented across virtually every human culture and has practical as well as energetic dimensions. Several plant-based smokes have documented antimicrobial and antifungal properties, providing a material-world correlate to the spiritual purification tradition.
A 2007 study published in the Journal of Ethnopharmacology found that burning a blend of medicinal herbs in an enclosed space for one hour reduced airborne bacterial counts by 94%, with the antimicrobial effects lasting up to 30 days. The researchers identified various plant volatiles including thymol, carvacrol, and other phenolic compounds as the active antimicrobial agents. White sage, which contains cineole and camphor, has similar documented antimicrobial properties. This gives the ancient practice of smoke purification a plausible physical mechanism alongside its spiritual dimensions.
For practical space clearing, move clockwise around the perimeter of a room while the incense burns, paying particular attention to corners (where stagnant energy accumulates in many traditions), doorways, and windows. Set a clear intention for what you are releasing and what quality you are establishing in the space. Open a window to allow the smoke and whatever it carries to exit the space rather than simply recirculating. Close the window after clearing to seal the energetic intention.
The Ethics of Sage and Palo Santo
White sage (Salvia apiana) is native to the coastal sage scrub of Southern California and northwestern Mexico and holds deep sacred significance in multiple Indigenous traditions. It has been overharvested due to commercial demand, and Indigenous communities have expressed concern about both environmental impacts and cultural appropriation. If you use white sage, source it ethically from Indigenous-owned producers or from cultivated rather than wildcrafted sources. Palo santo faces similar sustainability pressures. Both garden sage (Salvia officinalis) and cultivated lavender offer effective cleansing alternatives that carry no cultural appropriation concerns.
Making Your Own Incense
Making your own incense gives you complete control over ingredients, eliminates synthetic binders and fragrance oils, and creates a deeply personal aromatic practice. The simplest and most accessible starting point is loose herbal blends burned on charcoal.
Begin by gathering your raw materials: at least one resin (frankincense granules, benzoin, copal, or myrrh), one or two dried herbs or flowers (lavender, rosemary, rose petals, thyme, or sage), and optionally, a dried wood powder (sandalwood, cedarwood, or oud shavings for those with access). Resins create the smoke body and carry the blend. Herbs add aromatic complexity and specific plant energies. Wood powders deepen and extend the burn.
A basic starting formula: one part resin to two parts dried herbs or flowers. For example, one tablespoon of frankincense granules combined with two tablespoons of dried lavender and one tablespoon of dried rose petals. Grind the mixture coarsely in a mortar and pestle (leave some texture, do not powder completely). Burn small amounts (a pinch at a time) on charcoal discs and adjust the blend based on the aromatic result.
For stick incense, the process requires Makko powder as a natural binder. Combine your aromatic blend with Makko at roughly 50 to 60% Makko by weight, add small amounts of warm water, and mix to a stiff, workable dough. Roll the dough around pre-soaked bamboo sticks (or form coreless sticks between your palms). Dry for 24 to 48 hours in a cool, well-ventilated space before burning. The ratio of Makko to aromatics requires experimentation, as different plant materials hold moisture differently.
Beginner Loose Incense Blends to Try
- Sacred Space Blend: 2 parts frankincense, 1 part myrrh, 1 part dried cedar tips.
- Heart Opening Blend: 2 parts rose petals, 1 part benzoin resin, 1 part dried jasmine flowers.
- Grounding Blend: 1 part frankincense, 1 part dried vetiver root, 1 part patchouli leaves.
- Mental Clarity Blend: 2 parts dried rosemary, 1 part copal, 1 part dried lemon peel.
- Sleep and Rest Blend: 3 parts dried lavender, 1 part benzoin, small amount of chamomile flowers.
Store finished blends in glass jars with tight-fitting lids. Label with the date and ingredients. Well-stored blends retain aromatic quality for one to three years, though resins tend to maintain their potency longer than dried plant materials. Experiment seasonally, as different plant energies are associated with different times of year in most aromatic traditions.
Our Hermetic Synthesis Course covers aromatic ceremony, space clearing rituals, and the full spectrum of energy work practices.
Explore the CourseFrequently Asked Questions
What is the difference between incense sticks, cones, and loose resin?
Incense sticks mix aromatic material with a bamboo core and binding agent. They are convenient and consistent. Cones contain no bamboo core and produce more intense fragrance. Loose resin incense, burned on charcoal discs, is the most traditional form, releasing full aromatic complexity without synthetic binders. Resin is generally the highest quality option for ritual and ceremonial use.
Which incense is best for meditation?
Sandalwood is the most consistently documented for meditative focus, with research confirming its anxiety-reducing properties. Frankincense deepens breathing and has over 3,000 years of documented use in contemplative contexts. Nag Champa (sandalwood and champak) is widely associated with meditation spaces globally. Match the scent to your session's intention for most effective use.
Is incense smoke harmful to breathe?
Regular exposure in poorly ventilated spaces carries health risks similar to other combustion products. Key mitigations: ensure good ventilation (open window or door), use natural incense without synthetic fragrances or chemical binders, keep burning time moderate, and never burn incense where infants, people with asthma, or birds are present.
What incense did Hildegard von Bingen use medicinally?
Hildegard prescribed frankincense smoke for mental clarity and spiritual elevation, lavender smoke for headaches and nervous tension, rosemary fumigation for respiratory conditions, and sage for digestive complaints and atmospheric purification. Her 12th-century prescriptions align remarkably closely with modern aromatherapy research on these same plants.
How do I burn loose resin incense on charcoal?
Fill a heat-safe censer with sand for insulation. Hold a self-igniting charcoal disc with tongs and ignite one edge until sparks travel across it. Place in the sand bowl and wait two to three minutes for full heating. Add a small amount of resin on top. Add more in small increments as it burns away. Never leave burning charcoal unattended.
What incense is best for space clearing?
White sage (used respectfully and sourced ethically from Indigenous or cultivated sources) is the most widely known. Palo santo produces a warmer clearing smoke. Frankincense purifies sacred spaces in Catholic, Orthodox, and many esoteric traditions. Cedar and juniper are used in First Nations traditions. A 2007 study found medicinal herb smoke reduced airborne bacterial counts by 94%.
Can I make my own incense at home?
Yes. The easiest approach is loose herbal blends burned on charcoal: combine one part resin (frankincense, benzoin, or copal) with two to three parts dried herbs and flowers. Common beginner blends include frankincense and lavender (relaxation), copal and rosemary (clarity), and frankincense plus myrrh (sacred ceremony). Store in airtight glass jars away from heat and light.
What scents support specific spiritual purposes?
Sandalwood and frankincense for meditation. White sage and palo santo for clearing. Rose and jasmine for heart work. Vetiver, myrrh, and patchouli for grounding. Cinnamon and orange for energy and abundance. Lavender and chamomile for sleep and rest. Cedar and juniper for protection. Match your scent to your intention before lighting.
How long does an incense stick burn?
Standard sticks burn 20 to 45 minutes. Dhoop sticks (thicker, coreless) burn 45 to 90 minutes. Cones burn 15 to 30 minutes with more fragrance intensity. Coils burn several hours and are used in temples for continuous fragrance. One standard stick typically aligns well with a single meditation session.
How should I store incense to preserve quality?
Store in airtight containers away from direct light, heat, and humidity. Sunlight degrades essential oils rapidly, heat accelerates evaporation of aromatic compounds, and moisture causes mold. Keep sticks horizontal in sealed tubes. Store resins in glass jars with tight lids. Natural incense properly stored retains aromatic potency for two to five years.
Sources and References
- Dayrell-Reed, Frank. The Place of Incense in History and Religion. 1914.
- Hildegard von Bingen. Physica, 12th century CE. Translated by Priscilla Throop, Healing Arts Press, 1998.
- Nautiyal, C.S., et al. "Medicinal Smoke Reduces Airborne Bacteria." Journal of Ethnopharmacology, 2007.
- Moussaieff, A., et al. "Incensole Acetate, an Incense Component, Elicits Psychoactivity." FASEB Journal, 2008.
- Moss, M., et al. "Aromas of Rosemary and Lavender Essential Oils Differentially Affect Cognition." International Journal of Neuroscience, 2003.
- Toda, M. and Morimoto, K. "Effect of Lavender Aroma on Salivary Endocrinological Stress Markers." Archives of Oral Biology, 2008.
- Lis-Balchin, M. Aromatherapy Science: A Guide for Healthcare Professionals. Pharmaceutical Press, 2006.