Essential Oils and Hydrosols: Understanding the Difference
Essential Oils and Hydrosols
— Two different expressions of the same plant —
When people think of aromatherapy, essential oils are often the first thing that comes to mind. Hydrosol, on the other hand, are less widely understood. Even though many people have heard the term, their role and characteristics are often overlooked.
Through my own practice and daily use, working with both essential oils and hydrosols, I’ve come to realise that although they originate from the same plant, they are fundamentally different in nature.
In this post, I’d like to explore the difference between essential oils and hydrosols,and the unique role each one plays.
Hydrosols: the aromatic water from distillation
Hydrosols are aromatic waters produced during the steam distillation of essential oils. During distillation, volatile aromatic compounds separate into the oil phase (essential oil), while the remaining water becomes the hydrosol.
Because of this, hydrosols are sometimes described as a “by-product” of essential oils. However, the types of compounds they contain — and how they work — are very different from those found in essential oils.
The renewed appreciation of hydrosols
In the past, hydrosols received far less attention than essential oils. In recent years, however, their water-soluble components and gentle nature have been re-evaluated, particularly in skincare and everyday care.
They are now recognised as valuable tools for sensitive skin, delicate areas, and routines that require repeated, gentle application.
Chamazulene: a key example of the difference
A particularly clear example of the difference between essential oils and hydrosols is chamazulene, a compound known for its anti-inflammatory and soothing properties.
The deep blue colour of German chamomile essential oil comes from this compound.
Chamazulene:
- does not exist in the plant in its original form
- is created through chemical transformation during distillation
(from precursors such as matricin) - is fat-soluble, meaning it concentrates in the essential oil
and is largely absent from the hydrosol
Water-soluble compounds in hydrosols
Hydrosols, on the other hand, contain water-soluble compounds that are not present — or only present in trace amounts — in essential oils.
For example, Roman chamomile hydrosol contains flavonoids and other hydrophilic components, which provide gentle calming and anti-inflammatory effects.
Even when derived from the same plant:
- German chamomile essential oil offers targeted, concentrated support
- Roman chamomile hydrosol provides soft, everyday care
Their roles are clearly different.
When hydrosols are especially useful
Hydrosols are particularly helpful for:
- Gently caring for the face and neck
- Areas with thinner or more sensitive skin
- Mild care over larger areas such as the back or legs
- Light hydration and skin refreshment
- Daily, repeated skincare routines
- Children who are too young for essential oil use
They also offer a more accessible way to work with plants such as rose, jasmine, neroli, and helichrysum — essential oils that are often very expensive.
Essential oils and hydrosols work best together
Essential oils and hydrosols are not a matter of choosing one over the other. When their different properties are understood and used together, they allow the plant’s qualities to be expressed more fully and more gently.
The concentrated power of essential oils, and the softly diffusing nature of hydrosols, each have their own role. Used in synergy, they support a balanced, practical approach to aromatherapy that fits naturally into everyday life.
In my next blog post, I’ll look more closely at how hydrosols can be used in daily care, including gentle applications for children. I’ll also explore the different therapeutic properties of various hydrosols, and how their characteristics can support the skin and overall wellbeing.