A variety of mechanisms have been proposed for the reported effects of aromatherapy. It has been suggested that following placement of oil onto the skin, or breathing in fragrant air, the odor-sensing nerves in the nose are stimulated, sending impulses to the limbic system of the brain (a center for processing of emotions). A different theory is that some oils directly interact with hormones or enzymes in the blood, or stimulate the adrenal glands. Scientific research is limited in these areas, and it remains unclear how specific types of aromatherapy may work in the body.
There are more than 100 essential oils commonly used for aromatherapy. These oils are extracted from flowers (rose, narcissus), roots (orris), leaves and needles (eucalyptus, pine), resins (turpentine), seeds (caraway), fruits (lemon, lime), berries (cloves), bark (cinnamon) and wood (cedar). Many are obtained from familiar herbs and spices (basil, anise, nutmeg, cumin, oregano), and many are derived from substances related to herbal medicine (ginger, garlic, St. John's wort).
Agitation in patients with dementia:
Aromatherapy using essential oil of lemon balm (Melissa officinalis) may reduce agitation in people with severe dementia, when applied to the face and arms. Other research reports that steam inhalation of lavender aromatherapy may have similar effects. Overall, the evidence does suggest potential benefits.
Alopecia areata (hair loss):
Alopecia areata is a disorder in which the body's immune system attacks hair follicles, resulting in unpredictable patches of hair loss. Early evidence suggests a blend of essential oils rubbed into the scalp may show benefit.
Anxiety (lavender aromatherapy):
Lavender aromatherapy may be able to reduce anxiety. However, there have been conflicting results, and more study is needed in this area.
Anxiety (sandalwood aromatherapy in palliative care):
Lavender may contribute to reduced anxiety and improved mood, at least subjectively, but some other aromas, such as sandalwood, may not. More studies are needed to confirm these findings.
Anxiety/stress in intensive care unit patients (lavender aromatherapy):
It is unclear whether lavender aromatherapy reduces anxiety levels in intensive unit care patients.
There is not enough scientific evidence to recommend for or against the use of aromatherapy in arthritis patients.
Atopic eczema (children):
It is unclear whether aromatherapy might benefit children with atopic eczema.
Cancer (quality of life):
Aromatherapy is often used in people with chronic illnesses (frequently in combination with massage), with the intention to improve quality of life or well- being. There is not enough scientific evidence in this area.
Aromatherapy may be helpful during childbirth to relieve anxiety, pain, nausea, and/or vomiting or to strengthen contractions. It may also reduce pain perceived by first time mothers.
Chronic obstructive pulmonary disease (COPD):
Early evidence suggests that aromatherapy may aid mucus clearance in COPD. More studies are needed before conclusions about this application of aromatherapy can be made.
Early research in Guillian Barré syndrome patients show a possible benefit of aromatherapy massage for constipation, and rosemary, lemon, and peppermint essential oils may be beneficial in the elderly. Additional study is warranted to differentiate the effects of essential oils vs. massage.
Decongestant-expectorant/upper respiratory tract infection (eucalyptus aromatherapy):
Despite widespread use in over-the-counter agents and vapors, there is not enough scientific evidence to recommend use of eucalyptus oil as a decongestant-expectorant (by mouth or inhaled form).
There is not enough scientific evidence to recommend for or against the use of aromatherapy in patients with mild depression.
Abdominal aromatherapy massage with a combination of essential oils may reduce the intensity of menstrual cramps in women with dysmenorrhea. More research is needed in this area to identify the most effective essential oils.
Itching (pruritus) in dialysis patients:
Preliminary research reports reduced itching in dialysis patients receiving aromatherapy massage. Further research is necessary before a firm conclusion can be drawn.
Massage and skin care with and without aromatherapy improved relief and wellbeing in breast cancer patients. More study is needed in this area.
Nausea and vomiting (post-operative):
There is not enough scientific evidence to recommend for or against the use of aromatherapy in patients with post-surgery nausea.
Perineal discomfort after childbirth:
Early research on the use of essential oils in bath water or soap suggests limited or no benefit for post-partum perineal discomfort. More studies are needed before conclusions can be reached about this application of essential oils.
Aromatherapy is popularly used to improve mood. A preliminary study found that aromatherapy in first-time mothers had improved moods after aromatherapy. Higher quality research is needed in this area.
Sleep apnea (pediatric):
Early research suggests that pre-mature newborns with sleep apnea may benefit from aromatherapy. However, more data are needed before definitive recommendations can be made.
Sleep quality (adults):
Early research suggests that lavender may have general benefits for sleep quality and specific benefits for insomnia.
There is not enough scientific evidence to recommend for or against the use of aromatherapy in recovering stroke patients.
Early research suggests that aromatherapy may contribute to reduced pain intensity during dressing changes in wound care. More study is needed in this area.