Onion Uses and Plant Monograph

The common onion (Allium cepa) is one of the oldest cultivated plants in human history, believed to have been cultivated for at least 5,000 years. Onions are believed to have originated in regions including Iran, western Pakistan, and Central Asia.¹ The first recorded mention of onions comes from ancient Babylonian tablets around 1700–1600 BCE in what is now Iran. They also appear in India’s oldest Vedic texts, and the Sumerians were growing and cooking them 4,000 years ago.^2,3 In Ancient Egypt, onions were used in both culinary and medicinal contexts, and were even placed in tombs to honor the dead.⁴ The onion has made a global impact as a staple and dependable plant medicine.

Known for their sharp, pungent aroma and tear-inducing properties, onions are a fundamental base ingredient in cuisines around the globe. In addition, the plant is also deeply valued for its wide-ranging medicinal benefits from its antimicrobial to anti-inflammatory to cardioprotective properties. Despite their commonplace status, onions are a staple and powerhouse of plant healing.

Onion for Respiratory Health

Onions have long been celebrated for their powerful expectorant properties, playing a significant role in the treatment of respiratory ailments such as colds, coughs, bronchitis, and asthma. These benefits can be attributed primarily to the high concentration of sulfur compounds found in onions, particularly allicin, which gives the vegetable its pungent aroma and sharp taste. These sulfur-containing compounds act as mucolytics, meaning they help break down and thin mucus, making it easier to expel from the airways. This not only clears congestion but also reduces the severity and duration of respiratory infections.

Onions are also rich in antimicrobial properties, which enable them to fight off bacterial and viral infections that commonly lead to respiratory problems. One of the simplest and most time-tested remedies for a persistent cough involves creating a homemade onion syrup. By layering thinly sliced onions with honey or sugar, a syrup forms as the sugar draws out the onion’s juices, creating a natural remedy packed with soothing and antimicrobial effects. The honey or sugar further helps coat the throat, reducing irritation and providing relief from coughing fits.^5,6,7

Honey Onion Syrup Recipe

This old-fashioned remedy has been used for generations to soothe coughs and sore throats. With just onion and a bit of honey or sugar, you can make a gentle, effective syrup right in your kitchen.



Ingredients

• 1 medium onion (any variety)
• 2–3 tablespoons of raw honey (you can use sugar, if preferred)

Instructions

1. Peel the onion and slice it thinly into rounds or half-moons.
2. In a clean, glass jar or bowl place a layer of the onion slices on the bottom. Drizzle about 1 tablespoon of honey (or sprinkle with sugar) over the onion slices. Repeat the process, adding another layer of onions followed by honey or sugar, until you've used all the onion slices.
3. Cover the jar or bowl loosely and let the mixture sit at room temperature for 4–8 hours (or overnight). During this time, the honey or sugar will draw out the juices from the onion, creating a syrupy mixture.
4. Once the syrup has formed, strain out the onion slices and store the syrup in a sealed jar or container. Add a little extra raw honey if needed. 
5. Keep it in the refrigerator, where it will last for about 1 week.
6. Take 1–2 teaspoons of the syrup every few hours to help soothe a cough or sore throat. This remedy is safe for adults and children over the age of 1 (if using honey).

Yield: ~4 ounces of syrup

Special Consideration: honey should not be given to children under 1 year of age due to the risk of infant botulism. This rare but serious illness is caused by the bacteria Clostridium botulinum, which can be present in honey. You can use sugar in this recipe instead if needed.

Across many cultures, different types of folk remedies have tapped into the power of onions in even more hands-on ways. For example, crushed onions were often placed on the chest or feet of a sick individual to relieve chest congestion and draw out toxins. This practice aligns with the principles of reflexology, as the feet are believed to be connected to various parts of the body, including the lungs and respiratory system.⁸

In addition, onions contain quercetin, a powerful flavonoid that acts as an antioxidant. Quercetin is known to reduce inflammation in the airways and lungs, making it particularly helpful for individuals suffering from chronic respiratory conditions like asthma or bronchitis. Studies have shown that quercetin inhibits the production of histamines, which trigger allergic responses in the body, further aiding in the relief of asthma and other allergy-induced respiratory issues.⁹

Onion for Cardiovascular Support

The high content of flavonoid quercetin is one of the main reasons onion is considered a plant friend for heart and cardiovascular health. Research suggests that quercetin can help lower blood pressure, reduce cholesterol levels, and prevent plaque buildup in arteries, all of which contribute to reduced risk of cardiovascular diseases.¹⁰ Also, onions have blood-thinning properties due to their sulfur compounds, which act similarly to aspirin in reducing the risk of clot formation. Consuming raw onions regularly has been shown to support healthy blood circulation, decrease the likelihood of heart attacks and strokes, and enhance overall vascular health.¹¹

Onion for Immune Support

Onions are a natural immune booster due to their antimicrobial and antioxidant properties. The sulfur-containing compound allicin has potent antimicrobial effects that can help fight off bacterial and viral infections. Onions contain a small but beneficial amount of vitamin C, which is essential for the immune system’s proper functioning and helps the body combat infections. Throughout history, onions have been used in folk remedies or amulets to ward off illness and evil spirits. Historically across Western Europe, raw onions were often placed in homes to absorb harmful pathogens from the air, and people believed that keeping a sliced onion in a room could help prevent illness during epidemics.¹²

Oxymel, honeygar, Four Thieves vinegar, and fire cider are all variations of an immune boosting vinegar tincture that has been prepared for over 2,500 years. Fire Cider specifically is a type of oxymel, combining vinegar and raw honey as the base and adding horseradish, ginger, onion, garlic, and cayenne pepper to help ward off infections, colds, flu, and other bronchial ailments. The vinegar acts as a solvent, extracting medicinal minerals from plants much like alcohol does in traditional tinctures while both vinegar and honey serve to preserve the mixture. 

Although this preparation has been in use for centuries, the name “Fire Cider” can be attributed to Rosemary Gladstar, a renowned herbalist and educator, who coined the term in the late 1970s due to the potent, pungent ingredients in the recipe.¹³ You can learn more about her approach to making fire cider from her book Fire Cider!: 101 Zesty Recipes for Health-Boosting Remedies Made with Apple Cider Vinegar. Many herbalists and folk healers have since made their own variations for fire cider, some including more peppers and even fruit.  Today, fire cider has gained more popularity as a home remedy, particularly in the wake of the COVID-19 pandemic, and it is now produced commercially as well. 

Onion for Hair Growth

Onions have been recognized for their potential benefits in promoting hair growth for centuries, a practice rooted in traditional medicine across various cultures. In traditional Ayurvedic medicine, onion juice is often combined with other natural ingredients to enhance its effectiveness in treating hair loss.¹⁴ The sulfur compounds found in onions are thought to support collagen and improve blood circulation to the scalp, which may stimulate hair follicles and promote growth. Furthermore, onions are rich in antioxidants, particularly quercetin as mentioned, which helps combat free radicals and reduce inflammation in the scalp, creating a healthier environment for hair development.¹⁵ Despite the strong smell, modern uses of onion for hair growth have gained popularity, particularly in the realm of natural and holistic hair care, and can be found in a few commercial hair products.

Onion Juice Hair Treatment Recipe


Onion juice is a time-tested natural remedy believed to support hair growth and improve scalp health. This simple treatment can be made at home with just a few ingredients and a little patience.

Ingredients

• 1 large onion (any variety)
• Optional: a few drops of essential oil (like lavender or rosemary) to mask the onion smell

Instructions

1. Peel and chop the onion into small pieces.
2. Place the chopped onion in a blender or food processor. Blend until smooth.
3. Strain the mixture using a fine mesh strainer or cheesecloth to extract the juice. You should have about ¼ to ½ cup of onion juice.
4. If desired, add a few drops of your chosen essential oil to the onion juice to help reduce the strong onion scent. Mix well.
5. Using your fingers, apply the onion juice directly to your scalp, focusing on areas where you want to promote hair growth. Massage gently for a few minutes to stimulate blood circulation.It is recommended to part your hair into sections for easier application.
6. Allow the onion juice to sit on your scalp for 30–60 minutes. You can cover your hair with a shower cap to prevent dripping.
7. Rinse your hair thoroughly with a mild shampoo to remove the onion juice. You may need to wash twice to eliminate the scent completely.



Yield: ¼–½ cup onion juice 

Special Considerations: Onion juice, similar to cutting onions, can make one’s eyes tear intensely. Be cautious and do not allow onion juice to get into one’s eyes, if it does wash out immediately. One method to try and avoid this is to sit salon-style in a chair with your hair over the sink. Always do a patch test first to ensure you don’t have an allergic reaction to onion juice. Store any leftover juice in the refrigerator for up to a week, but it’s best to use fresh juice when possible.

Onion for Wound Healing

One of the lesser-known uses of onions is their ability to prevent scarring and promote wound healing due to their antimicrobial and anti-inflammatory properties. Onion extract, rich in sulfur compounds, is commonly used in commercial scar-reducing gels.¹⁶ When applied topically as a poultice, onions can help prevent infection, reduce inflammation, and promote faster healing of small cuts, burns, and insect bites.

Simple Onion Poultice Recipe


Onion poultices have long been used in folk remedies to support healing and reduce inflammation. This easy-to-make treatment draws on the natural antibacterial and soothing properties of onions.

Ingredients

• 1 medium to large onion
• Filtered water (optional)
• Cheesecloth or a clean cloth

Instructions

1. Peel and chop the onion into small pieces or slices. The more finely chopped, the better it will release its juices.
2. Place the chopped onion in a bowl. You can use a fork or a pestle to mash the onion slightly to release its juices. If you prefer a smoother consistency, you can blend the onion in a food processor.
3. If the mixture seems too dry, you can add a small amount of water to help it bind together. However, you want it to remain mostly onion pulp.
4. Transfer the mixture onto a piece of cheesecloth or a clean cloth. Fold the cloth to enclose the onion pulp securely.
5. Make sure the body area that is being treated is clean before applying, and then place the poultice directly onto the wound or scar. You can secure it in place with a bandage or medical tape, if necessary.
6. Keep the poultice on the area for about 20–30 minutes. You can repeat this process 2–3 times a day.
7. After removing the poultice, gently clean the area with warm water and pat it dry.

Special Considerations: always do a patch test first to ensure there’s no allergic reaction to the onion on the skin. This poultice is best used on minor wounds and scars. If the wound is severe or shows signs of infection, consult a healthcare professional.

Onion for Digestive Health

Included as a base or main ingredient of so many global cuisines, the dietary fiber and prebiotic compounds found in onions promote healthy digestion. Onions are a rich source of inulin, a type of soluble fiber that serves as food for beneficial gut bacteria.¹⁷ Inulin helps to balance the gut microbiome, improving digestion, nutrient absorption, and bowel regularity.¹⁸ Onions also contain compounds that stimulate the production of digestive enzymes, which can help alleviate indigestion and bloating. Traditionally, raw onions have been consumed to relieve symptoms of gastrointestinal discomfort and to support a healthy digestive system.

Onion in Culinary Traditions

Onions are a cornerstone in many culinary traditions worldwide. They serve as a foundational ingredient in various cuisines, from the sharp crunch of raw onions in fresh salads to the deep, sweet richness of caramelized onions in soups and stews to pickled onions as a side dish, onions play an essential role in elevating the flavor profiles of countless dishes.

In Indian cuisine, for example, onions are integral to the cooking process, forming the base of numerous curries and gravies. They are often sautéed with spices like cumin, coriander, and turmeric to create a complex, aromatic foundation that enriches the entire dish. Signature dishes such as chana masala and paneer tikka masala rely heavily on onions, where they are blended with tomatoes and a mix of spices to create a vibrant, flavorful sauce. Additionally, in biryani, onions are caramelized to add depth and sweetness, enhancing the rice and meat components.

French cuisine also prominently features onions, particularly in the classic dish French onion soup. In this recipe, onions are slowly caramelized over low heat until they reach a rich, golden-brown color, which develops a deep, savory sweetness. This forms the heart of the soup, complemented by beef broth and topped with a crusty layer of melted cheese. Another renowned dish found in France as well as Germany is flammekueche, also known as tarte flambée. It is a thin, crispy dough traditionally topped with crème fraîche, onions, and lardons. The onions, sliced thinly and baked at high heat, become tender and slightly caramelized, adding a sweet contrast to the creamy base and smoky bacon.

Latin American cooking also utilizes onions extensively, especially in the preparation called sofrito, a sauce made from a blend of onions, garlic, peppers, and cilantro, which serves as the flavor base for many stews, meat, and rice dishes such as ropa vieja, sancocho, and frijoles. Salsas, such as pico de gallo, and guacamole often incorporate raw red onions for added crunch and a mild sharpness that balances the creaminess of the avocado and the acidity of the tomatoes.

Pico de Gallo Recipe


Pico de gallo is a fresh, zesty salsa that adds a bright burst of flavor to just about anything. Made with simple ingredients, it’s quick to prepare and perfect for topping tacos, rice bowls, or enjoying with chips.

Ingredients

• 2-3 large ripe tomatoes, diced
• 1 medium red onion, finely chopped
• 1–2 jalapeño peppers or 1 serrano pepper, seeded and minced 
• ⅓ cup fresh cilantro, chopped
• Juice of 1 lime
• Kosher salt, to taste

Instructions

1. Dice the tomatoes, finely chop the red onion, and mince the peppers. If you prefer a milder salsa, remove the seeds from the jalapeño or serrano pepper before chopping.
2. In a mixing bowl, combine the diced tomatoes, chopped red onion, minced jalapeños, and chopped cilantro.
3. Squeeze the juice of one lime over the mixture. This not only adds flavor but also helps to preserve the freshness of the ingredients.
4. Sprinkle salt to taste. Start with a small amount and adjust according to your preference. Gently stir the ingredients together until well combined.
5. Let the pico de gallo sit for about 15–30 minutes to allow the flavors to meld together. You can also refrigerate it for a more chilled salsa.

Yield: 2½–3 cups (20–24 ounces)

Notes: Pico de gallo is best enjoyed as a fresh condiment and can be added to rice, tacos, grilled meat, chicken or fish, potatoes, or chips.

Botanically Speaking

Onions are typically cultivated as annuals for their edible bulbs. They feature a tall, hollow green stem that can grow anywhere from 12 to 36 inches in height, depending on the variety and growing conditions. The bulb, which is the most recognizable part of the onion, consists of fleshy, overlapping scales that grow and develop underground. Mature onions typically have bulbs ranging from 2 to 8 inches in diameter, with yellow onions usually measuring 2 to 4 inches, red onions 2 to 6 inches, and sweet onions potentially reaching up to 8 inches.¹⁹ The bulb’s outermost layer is dry and papery, while the inner scales are crisp and juicy.

Onions thrive in well-drained soil that is rich in organic matter and requires full sun for optimal growth. These plants are sensitive to waterlogged conditions, so proper drainage is crucial. They are usually harvested when the green tops begin to dry out and turn yellow, signaling that the bulb has reached full maturity. It is interesting to note that it is the sulfur compounds within onions that are responsible for the characteristic pungent smell of onions that can cause tearing when cutting. These compounds are released when the onion’s cells rupture.

Special Considerations

While onions are generally safe to consume, some individuals may experience gastrointestinal discomfort from eating them raw, especially in large quantities. Onions in both culinary and medicinal qualities may also interfere with blood-thinning medications due to their natural anticoagulant properties. 

Those with allergies to members of the Amaryllidaceae family, such as garlic or leeks, should exercise caution when consuming onions. 

Onions are generally considered safe to consume during pregnancy and while breastfeeding.

Written by Naomi Spector

Naomi is a Jewish herbalist, ethnobotanist, and educator based in Massachusetts, on Pawtucket and Wampanoag land. Some of her favorite plants include garlic, pomegranate, chamomile, mulberry, and cedar. She hopes through her work as an educator and community herbalist to help connect folks to the plant traditions of their ancestors. Her practice draws on Sefardi, Ashkenazi and Mediterranean plant medicine traditions. She provides holistic plant-based care (physical, emotional, mental, and spiritual) to those seeking root cause changes in their lifestyle. Learn more about her work here: https://www.bibiandni.com.

Footnotes

1. K.E. Lawande, 23 - Onion, Editor(s): K.V. Peter, In Woodhead Publishing Series in Food Science, Technology and Nutrition, Handbook of Herbs and Spices (Second Edition), Woodhead Publishing, 2012, Pages 417-429, ISBN 9780857090393, https://doi.org/10.1533/9780857095671.417.

2. Mehta, I. (2017) Origin and History of Onions, IOSR Journal Of Humanities And Social Science, 22(9):7-10

3. Teshika, J. D., Zakariyyah, A. M., Zengin, T. Z. G., Rengasamy, K. R. R., Pandian, S. K. & Fawzi, M. M. (2018) Traditional and modern uses of onion bulb (Allium cepa L.): a systematic review, Critical Reviews in Food Science and Nutrition, DOI: 10.1080/10408398.2018.1499074

4. Cramer, Chris. “NMSU: Onion Breeding Program at NMSU - History.” Onion.nmsu.edu, 2024, onion.nmsu.edu/history.html.

5. Dorrigiv, Mahyar et al. “Onion (Allium cepa) and its Main Constituents as Antidotes or Protective Agents against Natural or Chemical Toxicities: A Comprehensive Review.” Iranian journal of pharmaceutical research : IJPR vol. 20,1 (2021): 3-26. doi:10.22037/ijpr.2020.112773.13940

6. Dorrigiv, Mahyar et al. “Onion (Allium cepa) and its Main Constituents as Antidotes or Protective Agents against Natural or Chemical Toxicities: A Comprehensive Review.” Iranian journal of pharmaceutical research : IJPR vol. 20,1 (2021): 3-26. doi:10.22037/ijpr.2020.112773.13940

7. Chakraborty, Arka Jyoti et al. “Allium cepa: A Treasure of Bioactive Phytochemicals with Prospective Health Benefits.” Evidence-based complementary and alternative medicine : eCAM vol. 2022 4586318. 18 Jan. 2022, doi:10.1155/2022/4586318.

8. Jacquelyn , Jacquelyn . “Onion in Sock: Cold and Flu Treatment.” Healthline, 17 May 2017, www.healthline.com/health/cold-flu/onion-in-sock.

9. Nishimura, Mie et al. “Effect of Daily Ingestion of Quercetin-Rich Onion Powder for 12 Weeks on Visceral Fat: A Randomised, Double-Blind, Placebo-Controlled, Parallel-Group Study.” Nutrients vol. 12,1 91. 28 Dec. 2019, doi:10.3390/nu12010091

10. Nishimura, Mie et al. “Effect of Daily Ingestion of Quercetin-Rich Onion Powder for 12 Weeks on Visceral Fat: A Randomised, Double-Blind, Placebo-Controlled, Parallel-Group Study.” Nutrients vol. 12,1 91. 28 Dec. 2019, doi:10.3390/nu12010091

11. Lang, Ariane. “Do Onions Have Any Downsides or Side Effects?” Healthline, 19 July 2021, www.healthline.com/nutrition/disadvantages-of-onion.

12. Schwarcz, Joe. “Is It True That Onions Can Absorb Bacteria?” Office for Science and Society, 20 Mar. 2017, www.mcgill.ca/oss/article/health-you-asked/it-true-onions-can-absorb-bacteria.

13. McCarney, Tre. “Fire Cider: Food as Medicine.” Shelburne Farms, 2025, shelburnefarms.org/about/news-and-stories/fire-cider-food-medicine. Accessed 2 Mar. 2025.

14. Shams, Hiba, M. Mushraff Ali Khan, and Anupama Koneru. "A Critical Analysis of the Usage of Herbal Products Amidst South Indian Population for the Treatment of Alopecia." Biosciences Biotechnology Research Asia 20.2 (2023): 561-570.

15. Sharquie, Khalifa E, and Hala K Al-Obaidi. “Onion juice (Allium cepa L.), a new topical treatment for alopecia areata.” The Journal of dermatology vol. 29,6 (2002): 343-6. doi:10.1111/j.1346-8138.2002.tb00277.x

16. Chong Wee Foo, Payam Tristani-Firouzi, Topical Modalities for Treatment and Prevention of Postsurgical Hypertrophic Scars, Facial Plastic Surgery Clinics of North America, Volume 19, Issue 3, 2011, Pages 551-557, ISSN 1064-7406, https://doi.org/10.1016/j.fsc.2011.06.008.

17. Semeco, Arlene. “The 20 Best Prebiotic Foods You Should Eat.” Healthline, Healthline Media, 31 Oct. 2023, www.healthline.com/nutrition/19-best-prebiotic-foods#onions.

18. Sheng, Wei et al. “Immunomodulatory effects of inulin and its intestinal metabolites.” Frontiers in immunology vol. 14 1224092. 10 Aug. 2023, doi:10.3389/fimmu.2023.1224092

19. The Editors of Encyclopaedia Britannica. “Onion | Plant | Britannica.” Encyclopædia Britannica, 2019, www.britannica.com/plant/onion-plant.