**6. Therapeutic benefits of essential oils**

Many plant essential oils are used as medicine for hundreds of years and have demonstrated several health benefits, including effects on infectious, chronic, and acute diseases. The medical preparations made with plant essential oils as well as their single constituents applied in the therapy of human infectious diseases are well documented. However, the selection of suitable safe oil and the determination of the best efficient dose should be taken into consideration to avoid any side effects when they are applied [41]. The action of volatile oils begins by entering the human body through three possible ways including direct absorption through inhalation, ingestion, or diffusion through the skin tissue.

**6.2 Inhalation**

*Different classes of volatile oil.*

*Aromatherapy as Complementary Medicine DOI: http://dx.doi.org/10.5772/intechopen.92021*

**Figure 2.**

it [46–48].

**6.3 Ingestion**

**113**

Volatile oils enter the body through the respiratory system. Due to their volatile ability, they can be inhaled easily through the upper respiratory tract and enter the lungs, by which it can be spread to the blood stream. In general, the respiratory tract is considered to be the most easiest way of entry, followed by the dermal pathway [45]. Inhalation of essential oils has given rise to olfactory aromatherapy, where simple inhalation has resulted in enhanced emotional wellness, calmness, relaxation, or rejuvenation of the human body. The release of stress is welded with pleasurable scents which unlock odor memories. Essential oils are complemented to medical treatment and can never be taken as a replacement for

Oral ingestion of essential oils needs to be done carefully due to the possible toxicity of some oils. Ingested volatile oil compounds and/or their metabolites may then be absorbed and delivered to the rest of the body and then distributed to different organs. Once volatile oil are entered in to the body, they create their therapeutic effect through physiological functions (**Table 3**). For example, *Roman chamomile* is extensively used to relieve pain from physical conditions, menstrual

cramps, and tension with its application on the lower abdomen [49–52].

**Figure 1.** *Different classes of volatile oil.*
