Essential Oils: The Complete Guide

By the Gstrein family · Viworo, Lana (South Tyrol) · updated June 2026

In short: essential oils are highly concentrated, volatile plant extracts obtained by steam distillation or cold pressing. They contain the plant's characteristic aroma molecules and are used mainly in aromatherapy (diffusing and inhalation) and – well diluted in a carrier oil – on the skin. A few drops are enough. This guide brings it all together: what they are, how they work, how to choose them and how to use them safely.

What essential oils are

An essential oil is the concentrated essence of an aromatic plant: the volatile liquid that holds the scent and characteristic compounds of flowers, leaves, roots, bark, resins or peels. It is obtained from plant material – in the case of our oils, from organic cultivation.

The key word is concentration: a single bottle requires large amounts of plant material. That is why essential oils are never used «by the spoonful», but drop by drop.

How they are obtained

• Steam distillation: the most common method. Steam passes through the plant, carries the aromatic substances along, and after cooling the oil separates from the water. Gentle and proven over centuries.
• Cold pressing: reserved for citrus oils (orange, lemon, bergamot). The peels are pressed mechanically, without heat, so the fresh notes stay intact.

How they work

Essential oils reach the body in two main ways:

• Smell: inhaled aroma molecules reach the limbic system – the brain area linked to emotions and memories – through the nasal mucosa. This is why a scent can calm or invigorate within seconds.
• Through the skin: diluted in a carrier oil and applied (for example in a massage), they are absorbed gradually. Never neat on the skin.

The science in brief: the molecule groups

The aroma and character of every oil depend on its composition. The most common groups:

• Monoterpenes (citrus, pine, cypress) – fresh, airy, invigorating notes.
• Esters (true lavender, Roman chamomile) – soft, relaxing notes, popular for the evening.
• Phenols and aldehydes (oregano, thyme, Litsea cubeba, melissa) – intense molecules; use well diluted.
• Oxides (eucalyptus, rosemary) – balsamic, airy notes, welcome in the cold season.

Knowing the groups helps you compose balanced blends and understand why some oils should be dosed more carefully.

The 5 essential oils to start with

If you are starting from scratch, these five cover almost every everyday need:

1. True Lavender: the all-rounder. Soft and floral, perfect for the evening and a calm atmosphere.
2. Peppermint: fresh and invigorating, ideal for studying or moments of tiredness.
3. Tea Tree: the purifying classic, useful for room and skin care.
4. Lemon: a lively citrus that freshens the air and lifts the mood.
5. Eucalyptus: balsamic and airy, the companion of the cold season in the diffuser or sauna.

How to use them (in practice)

• Diffusing: 4–6 drops in an ultrasonic diffuser scent a room for hours, without heat.
• Quick inhalation: 1–2 drops on a tissue, or a few drops in a bowl of warm water.
• On the skin (diluted): for a massage, roughly 2–3 drops of essential oil per 10 ml of carrier oil (almond, jojoba). For the face, use lower amounts.
• Bath: never add neat drops to the water – first emulsify with a spoon of carrier oil or salt.

For exact ratios see our dosage guide.

Safety: the golden rules

• Never neat on the skin: always diluted in a carrier oil.
• Do a patch test before first use.
• Keep away from eyes and mucous membranes; store tightly closed, away from light and heat.
• During pregnancy, breastfeeding, with small children or ongoing treatments: ask your doctor first.

Learn more in the full safety guidelines.

How to recognise a quality essential oil

• 100% pure and without diluents or synthetic oils.
• Botanical name in Latin on the label (e.g. Lavandula angustifolia) – it shows exactly which plant it is.
• Origin and plant part stated.
• Dark glass: protects the oil from light.
• Be wary of prices that are too low: a lemon and a rose cannot cost the same.

Versatile uses

Once you feel confident, essential oils accompany many moments: a diffuser running while you work, a relaxing blend in the evening, a homemade massage oil, room air freshened in seconds, an airier sauna. Find ready-made ideas in our free recipes and in the guide to essential oils in the sauna.

Frequently asked questions

What is the difference between an essential oil and a carrier oil?

The essential oil is the concentrated, volatile aromatic extract of the plant. The carrier oil (sweet almond, jojoba) is a fatty vegetable oil used to dilute the essential oil before applying it to the skin.

Can they be used neat on the skin?

No. Essential oils are very concentrated and must always be diluted in a carrier oil. A patch test before first use is recommended.

How many drops do you need in a diffuser?

Usually 4–6 drops are enough for a room. Better to start with a few and increase only if needed.

Can essential oils be ingested?

They are intended for aromatic and external use. For any other use, consult a qualified professional.

How should they be stored?

In dark glass bottles, tightly closed, away from light and heat. Stored well, citrus oils last about 1–2 years, many other oils even longer.

Sources and further reading

• Tisserand R., Young R. (2014). Essential Oil Safety, 2nd ed., Churchill Livingstone.
• Bäumler S. (2021). Heilpflanzenpraxis Heute – monographs on distillation and composition.
• ISO 9235 – Natural aromatic raw materials: definitions.

See also: Aromatherapy · History of essential oils.