What is a Hydrosol?

Although many herbalists, aromatherapists, and cosmetic formulators use hydrosols, they are not as well known in the general public. Hydrosols are amazing ingredients with many different benefits and uses. I enjoy using them in herbalism, aromatherapy, and skin and hair care formulation.

Hydrosols do not always have the same chemistry, properties, safety, and shelf life as herbs and essential oils. But they are an integral part of western herbalism, aromatherapy, and natural formulation. In this primer, you’ll learn the basics of hydrosols and how to use them.

What is a Hydrosol?

Hydrosols are one of the products of distillation. Many people know that steam distillation of plants can yield essential oils. But not everyone is familiar with the other product of distillation, which is a hydrosol. Hydrosols are produced during the earliest part of plant distillation¹ and they are non-alcoholic distillates.^2,3

Hydrosols are mostly water, but they are composed of water-soluble chemical components. If aromatic plants are distilled, then hydrosols will also have micro amounts of essential oil components. Hydrosols may contain about 0.02%^4,5,6 to 0.05%⁷ of essential oil constituents.

Herbalism and aromatherapy pioneer Jeanne Rose was the first person to use the term “hydrosol” for aromatic plant distillates in 1990.^8,9 Hydrosol was originally a term used in the gold industry.¹⁰ “Hydro” means water and “sol” means solution.^11,12 Hydrosols are known by other names such as hydrolats, distillates, aromatic waters, or floral waters (if they are made from flowers). The term hydrolat is usually used in Europe while US herbalists and aromatherapists tend to use the word hydrosol.

What is the Difference Between Hydrosol and Flower Water?

Although the flower hydrosols are occasionally called floral waters, not all floral waters are hydrosols. Some people call other types of herbal or aromatic preparations “floral waters,” like infusions (strong medicinal teas), essential oils sprays (sprays made with essential oils, distilled water, a solubilizer, and a preservative), or other plant extracts added to water. These types of floral waters are not the same thing as hydrosols. From time to time, I have seen hydrosols referred to as aromatic waters, but this term is not commonly used much in herbalism or aromatherapy.

Hydrosols can be distilled from aromatic plants that produce essential oils, as well as non-aromatic plants that do not yield essential oils during distillation. Examples of hydrosols from essential oil yielding plants are chamomile, lavender, rose, and peppermint. A couple hydrosols from plants that do not contain essential oils are witch hazel and cucumber.

Hydrosols and Essential Oils

The aroma of hydrosols is not always the same as its essential oil or the herb. For example, lavender (Lavandula angustifolia) hydrosol does not smell exactly like its essential oil. While it still is reminiscent of “lavender,” it generally does not have the same aroma as the essential oil. To my nose, the aroma of lavender hydrosol is more herbaceous or green. It is not as floral or as sweet as its essential oil.

Many hydrosols are the byproducts of essential oil production. In other words, the distiller has focused on distilling for the essential oil and not the hydrosol. Different distillation techniques are used when you are distilling for the essential oil than when you are distilling for the hydrosol. I recommend purchasing hydrosols in which the plants are distilled for the hydrosols. They are often much higher quality in composition as well as aroma.

Understanding Hydrosol Chemistry

All hydrosols are acidic. Hydrosols have a pH between 3.0 to 6.5¹³ depending on the distillate, season, crop, region, distillation methods, and other factors. Distiller and hydrosol researcher Ann Harman notes that there isn’t much data that confirms what the typical pH range is for each type of hydrosol.¹⁴ The pH range of one distiller’s rose hydrosol might be different than another distiller’s rose hydrosol.

The chemical composition of hydrosols is different than essential oils and herbal preparations. Their chemistry is not completely known yet, though there is some research which has identified several components and chemical families. Hydrosols contain water-soluble chemical constituents. Hydrosols are composed of acids,^15,16 phenols,^17,18 ketones,^19,20 aldehydes,^21,22 alcohols^23,24 (such as monoterpenols and sesquiterpenols²⁵), oxides,²⁶ and coumarins.²⁷ They contain little to no terpenes.²⁸ They do not contain esters,²⁹ bitter components,³⁰ or tannic acid.³¹

The State of Hydrosol Research

Although there has been some hydrosol research, hydrosols have not been scientifically studied that much. The majority of the existing studies are on their antimicrobial abilities, antioxidant properties, and chemical composition, but there is still a lot that we don’t know about their chemistry or properties. There are a few studies that have investigated other properties but they are far and few between. Their known benefits were initially largely extrapolated from knowledge about other herbal preparations or essential oil uses.

Then herbalists and aromatherapists experimented with distillates in their practices to figure out their actions and effectiveness. Most of the accepted information is based on anecdotal research. Many herbalists, aromatherapists, and distillers have offered their insights into hydrosol benefits. I have researched and experimented with over 70 hydrosols since I began studying herbalism and aromatherapy over 18 years ago. I have used them in many case studies to deduce their uses.

Diving into Hydrosol Safety

For adults and older children, hydrosols are typically applied to the skin undiluted. For babies and young children (under the age of 3), there may be certain ones you might not want to use, depending on their age. Aromatherapy pioneer Andrea Butje often suggests using hydrosols on babies and young kids, but she does not mention diluting them.³² Jeanne Rose suggests diluting hydrosols to 50% to 75% for kids over age 6, and for children younger than age 6 to dilute them even more or avoid using them.³³

However, if you dilute hydrosols, then that reduces their shelf life. If you choose to dilute hydrosols, then dilute them with distilled water, and only dilute enough for one use and use it immediately.

Storage and Shelf Life of Hydrosols

Although hydrosols are water based, they typically are sold unpreserved from herbalism and aromatherapy companies. Hydrosols are sterile straight from the still. However, since they are water based, they can easily become contaminated. Hydrosols have a shelf life of about 1 to 2 years, especially when properly stored and handled. But they are perishable and they can go bad in days. They need to be handled and stored with care.

I highly suggest refrigerating or freezing hydrosols to help extend their shelf life. I usually refrigerate small amounts of hydrosols or ones that I use up quickly. I store 4- to 8-ounce bottles in the fridge, and I fill up 1-ounce spray bottles to keep at room temperature. If I have not used the 1-ounce spray bottles in a couple weeks, then I stick them back in the fridge. If I buy larger amounts of hydrosols, such as 16 ounces to a gallon, I usually package them into smaller bottles and place one of the bottles in the fridge, and then I freeze the excess. I simply defrost what I need later.

Some companies may add preservatives or ingredients to hydrosols that help improve their shelf life, especially for the ones that tend to go bad quickly. For example, one of the most popular herbal preparations is witch hazel extract. Witch hazel extract is the distillate with 14% alcohol added. There are other types of products known as “witch hazel extract,” but when herbalists refer to witch hazel extract, we usually mean the distillate plus alcohol.

When you are first trying hydrosols, it is best to try samples or smaller sizes before investing in bigger sizes. I suggest only trying 1 to 4 ounces before buying a larger amount. This way you can try different hydrosols to see what works best for you.

Here are some frequently asked questions about hydrosols....

Can I use a hydrosol as a facial toner?

Yes, you can use a hydrosol as a facial toner before applying moisturizer. Some hydrosols that make for a lovely skin toner include lavender hydrosol, rose hydrosol, and chamomile hydrosol. Hydrosols are gentle facial toners for sensitive skin. 

Is rose water a hydrosol?

Yes, rose water is a hydrosol made by distilling rose petals.

Written by Li Wong

Li Wong is a qualified vintage herbalist, qualified vintage aromatherapist, professional cosmetic formulator, environmental scientist/botanist, and natural perfumer. Li is the founder and educator at Plant Alkemie Institute of Holistic Botanical Studies. She is passionate about helping people reconnect to nature and deepening their understanding and knowledge of plants. She has been studying plants for a few decades. www.plantalkemie.com

Footnotes

1. Rose, Jeanne. 2007. Hydrosols & Aromatic Waters–A Collection of Data All About Hydrosols and Their Distillation. Chapter 1: History of Aromatic Waters. Jeanne Rose Aromatherapy and the Institute of Aromatic & Herbal Studies in collaboration with the Aromatic Plant Project. San Francisco, CA. p.15. ↩
2. Rose, Jeanne. 2007. Hydrosols & Aromatic Waters–A Collection of Data All About Hydrosols and Their Distillation. Chapter 1: History of Aromatic Waters. Jeanne Rose Aromatherapy and the Institute of Aromatic & Herbal Studies in collaboration with the Aromatic Plant Project. San Francisco, CA. p.15. ↩
3. Rose, Jeanne. 1998 to 2014. Hydrosols: Notes on Hydrosols. The Aromatic Plant Project. San Francisco, CA. Accessed May 15, 2020 at http://www.aromaticplantproject.com/hydrosols.html#floralhydrosols. ↩
4. Ibid. ↩
5. Rose, Jeanne. 2007. Hydrosols & Aromatic Waters–A Collection of Data All About Hydrosols and Their Distillation. Chapter 4: How Hydrosols are Produced. Aromatherapy Hydrosols or Hydrolates: The Water Solutions from Steam Distillation Containing the Original Essential Oils & All Water Soluble Therapeutic Compounds. Jeanne Rose Aromatherapy and the Institute of Aromatic & Herbal Studies in collaboration with the Aromatic Plant Project. San Francisco, CA. p. 40. ↩
6. Price, Shirley, Len Price, and Penny Price. 2020. Aromatherapy For Health Care Professionals, 5th edition. Chapter 5-Hydrolats: The Essential Waters. What are Hydrolats? Elsevier. London, UK. p. 91. ↩
7. Price, Shirley, Len Price, and Penny Price. 2020. Aromatherapy For Health Care Professionals, 5th edition. Chapter 5-Hydrolats: The Essential Waters. What are Hydrolats? Elsevier. London, UK. p. 91. ↩
8. Rose, Jeanne. 2007. Hydrosols & Aromatic Waters–A Collection of Data All About Hydrosols and Their Distillation. Chapter 1: History of Aromatic Waters. Jeanne Rose Aromatherapy and the Institute of Aromatic & Herbal Studies in collaboration with the Aromatic Plant Project. San Francisco, CA. p.15. ↩
9. Rose, Jeanne. 2007. Hydrosols & Aromatic Waters–A Collection of Data All About Hydrosols and Their Distillation. Chapter 2-The History of the Current word usage-Hydrosol. Jeanne Rose Aromatherapy and the Institute of Aromatic & Herbal Studies in collaboration with the Aromatic Plant Project. San Francisco, CA. p. 26. ↩
10. Rose, Jeanne. 2007. Hydrosols & Aromatic Waters–A Collection of Data All About Hydrosols and Their Distillation. Chapter 2-The History of the Current word usage-Hydrosol. Jeanne Rose Aromatherapy and the Institute of Aromatic & Herbal Studies in collaboration with the Aromatic Plant Project. San Francisco, CA. p. 26. ↩
11. Rose, Jeanne. 2007. Hydrosols & Aromatic Waters–A Collection of Data All About Hydrosols and Their Distillation. Chapter 1: History of Aromatic Waters. Jeanne Rose Aromatherapy and the Institute of Aromatic & Herbal Studies in collaboration with the Aromatic Plant Project. San Francisco, CA. p.15. ↩
12. Rose, Jeanne. 2007. Hydrosols & Aromatic Waters–A Collection of Data All About Hydrosols and Their Distillation. Chapter 2-The History of the Current word usage-Hydrosol. Jeanne Rose Aromatherapy and the Institute of Aromatic & Herbal Studies in collaboration with the Aromatic Plant Project. San Francisco, CA. p. 26. ↩
13. Harman, Ann. 2015. Harvest To Hydrosol: Distill Your Own Exquisite Essential Oils At Home. Chapter 4–Nuts and Bolts: pH And Meters-pH Ranges. IAG Botanicals LLC dba botANNicals. Fruitland, WA. p. 70. ↩
14. Harman, Ann. 2015. Harvest To Hydrosol: Distill Your Own Exquisite Essential Oils At Home. Chapter 4–Nuts and Bolts: pH And Meters-pH Ranges. IAG Botanicals LLC dba botANNicals. Fruitland, WA. p. 70. ↩
15. Harman, Ann. 2015. Harvest To Hydrosol: Distill Your Own Exquisite Essential Oils At Home. Chapter 4—Nuts and Bolts: Water Solubles. IAG Botanicals LLC dba botANNicals. Fruitland, WA. p. 91 ↩
16. Skipper, Cathy. 2016 to 2020. Hydrosols Certification Program. Module 3—Chemistry. Biochemistry of Hydrosols and Chemical Families. AromaGnosis. Arroyo Seco, NM. ↩
17. Harman, Ann. 2015. Harvest To Hydrosol: Distill Your Own Exquisite Essential Oils At Home. Chapter 4—Nuts and Bolts: Water Solubles. IAG Botanicals LLC dba botANNicals. Fruitland, WA. p. 91 ↩
18. Skipper, Cathy. 2016 to 2020. Hydrosols Certification Program. Module 3—Chemistry. Biochemistry of Hydrosols and Chemical Families. AromaGnosis. Arroyo Seco, NM. ↩
19. Harman, Ann. 2015. Harvest To Hydrosol: Distill Your Own Exquisite Essential Oils At Home. Chapter 4—Nuts and Bolts: Water Solubles. IAG Botanicals LLC dba botANNicals. Fruitland, WA. p. 91 ↩
20. Skipper, Cathy. 2016 to 2020. Hydrosols Certification Program. Module 3—Chemistry. Biochemistry of Hydrosols and Chemical Families. AromaGnosis. Arroyo Seco, NM. ↩
21. Harman, Ann. 2015. Harvest To Hydrosol: Distill Your Own Exquisite Essential Oils At Home. Chapter 4—Nuts and Bolts: Water Solubles. IAG Botanicals LLC dba botANNicals. Fruitland, WA. p. 91 ↩
22. Skipper, Cathy. 2016 to 2020. Hydrosols Certification Program. Module 3—Chemistry. Biochemistry of Hydrosols and Chemical Families. AromaGnosis. Arroyo Seco, NM. ↩
23. Harman, Ann. 2015. Harvest To Hydrosol: Distill Your Own Exquisite Essential Oils At Home. Chapter 4—Nuts and Bolts: Water Solubles. IAG Botanicals LLC dba botANNicals. Fruitland, WA. p. 91 ↩
24. Skipper, Cathy. 2016 to 2020. Hydrosols Certification Program. Module 3—Chemistry. Biochemistry of Hydrosols and Chemical Families. AromaGnosis. Arroyo Seco, NM. ↩
25. Ibid. ↩
26. Ibid. ↩
27. Ibid. ↩
28. Rose, Jeanne. 2007. Hydrosols & Aromatic Waters–A Collection of Data All About Hydrosols and Their Distillation. Chapter 4: How Hydrosols are Produced. Aromatherapy Hydrosols or Hydrolates: The Water Solutions from Steam Distillation Containing the Original Essential Oils & All Water Soluble Therapeutic Compounds. Jeanne Rose Aromatherapy and the Institute of Aromatic & Herbal Studies in collaboration with the Aromatic Plant Project. San Francisco, CA. p. 40. ↩
29. Skipper, Cathy. 2016 to 2020. Hydrosols Certification Program. Module 3—Chemistry. Biochemistry of Hydrosols and Chemical Families. AromaGnosis. Arroyo Seco, NM. ↩
30. Price, Shirley, Len Price, and Penny Price. 2020. Aromatherapy For Health Care Professionals, 5th edition. Chapter 5-Hydrolats: The Essential Waters. Introduction. Elsevier. London, UK. p. 89. ↩
31. Ibid. ↩
32. Butje, Andrea. 2017. The Heart of Aromatherapy. Using Essential Oils Safely: Babies and Children. Hay House, Inc. Carlsbad, California. p.15. ↩
33. Rose, Jeanne. 2015. Hydrosols-Floral & Herbal Hydrosols For Children. “Hydrosols” – Herbs & Aromatherapy (Jeanne Rose’s Facebook group). Accessed May 15, 2020 at https://www.facebook.com/groups/hydrosols/files/. ↩