Copper Sulfate (Bluestone): Uses, Remedies and Risks

Author: Ian C. Langtree - Writer/Editor for Disabled World (DW)
Published: 10 Sep 2014 - Updated: 27 Sep 2026
Publication Type: Informative

Table of Contents:
Synopsis - Definition - Overview - FAQs - Insights, Updates - Related Content

Synopsis

This information covers copper sulfate - commonly called bluestone or blue vitriol - detailing its wide range of historical, industrial, agricultural, and medical applications, alongside serious safety precautions every user should know. From its role as an antifungal agent and fungicide to its historical use in folk and home remedies for conditions such as warts, toenail fungus, and canker sores, the article draws on established chemical data and historical medical records to give readers a factual grounding in what this compound is, what it has been used for, and where its very real dangers lie. It is particularly relevant to farmers, gardeners, hobbyists, and anyone who may encounter copper sulfate in a home or occupational setting, including older adults and caregivers who may come across references to these traditional remedies in older texts.

At a Glance

1 - Sheep are still walked through copper sulfate foot baths to prevent and treat foot rot.
2 - Blood can be screened for anemia by dropping it into a copper sulfate solution of known specific gravity.
3 - Pouring 1 to 2 pounds of crystals into the toilet nearest the sewer line has long been used to kill tree roots growing into pipes.
4 - Heavy use of copper-based fungicides in orchards has wiped out most animal life in the soil, including large earthworms. Bordeaux mixture also puts bees at risk.

Topic Definition

Copper Sulfate: Bluestone is the common name for copper sulfate, a copper salt most often seen as bright blue crystals of copper sulfate pentahydrate. Farm supply stores have carried it for generations. Farmers, orchard growers, and pool owners have used it to kill fungus, algae, and invasive roots, and it has been used in industry for electroplating, printmaking, and dyeing. Before modern medicine, it was a household cure for wounds, warts, and skin infections in both people and livestock. It works because copper ions are toxic to fungi, bacteria, and plant tissue, and that same toxicity makes it dangerous to people, pets, fish, and soil life. It needs careful handling, protective gear, and proper storage.

Overview

What is Copper Sulphate?

Copper sulfate, also known as blue vitriol, Salzburg vitriol, Roman vitriol, blue copperas, or bluestone, is a chemical compound comprised of Copper, Sulphur and Oxygen whose formula is CuSO4. Copper Sulphate is an odorless crystalline substance, electric blue in color, highly toxic, and not safe to work with. It is produced industrially by treating copper metal with hot concentrated sulfuric acid or its oxides with dilute sulfuric acid. For laboratory use, copper sulfate is usually purchased. The anhydrous form occurs as a rare mineral known as chalcocyanite. The hydrated copper sulfate occurs in nature as chalcanthite (pentahydrate), and two other rare ones: bonattite (trihydrate) and boothite (heptahydrate).

Copper sulfate was used in the past as an emetic, (An agent that induces vomiting). It is now considered too toxic for this use, however, it is still listed as an antidote in the World Health Organization's Anatomical Therapeutic Chemical Classification System.

Caution!

Many of these home cures using Bluestone come from old medical texts and home remedy books. Some of the suggestions are also found on the Internet. We have NOT tried any of the cures listed below and suggest you don't either, they are listed purely for historical and entertainment purposes. Always consult a doctor before using any home remedy, especially if you are taking medication of any sort. (See Warnings and Precautions Further Down This Page)

In some countries, this substance may only be approved for veterinary use.

Uses for Copper Sulfate (Bluestone)

Antiseptic agent
In electroplating processes.
Antifungal agent for topical use
Treatment of copper deficiency
Curing "Proud Flesh" on Horses.
Etching - Copper sulfate is also used to etch zinc plates for intaglio printmaking.
Dyes - Copper sulfate can also be used as a mordant in vegetable dyeing. It often highlights the green tints of the specific dyes.
Copper sulfate is used to test blood for anemia. The blood is tested by dropping it into a solution of copper sulfate of known specific gravity.
Copper sulfate crystals is still used today dissolved in water in a "foot bath" for sheep to pass through as a prevention and cure for "foot rot".
School Projects - Growing crystals of Copper Sulfate is one of the more common science projects for middle school and high school children.
Copper sulfate is (was) one of the ingredients of the styptic powder, Kwik Stop, which is/was widely used to stop superficial bleeding in animals.
Copper sulfate can be applied to your plants before disease starts as a preventative as well as when you begin to notice the dark spots of infection show.
As an additive to swimming pools to clear the water and eliminate algae. Put half a teaspoon every 10 to 15 days into the skimmer box and let the pool pump run for at least 12 hours. (You can swim right away)
Copper sulfate pentahydrate is a fungicide. However, some fungi are capable of adapting to elevated levels of copper ions. Mixed with lime it is called Bordeaux mixture and used to control fungus on grapes, melons, and other berries.
Bluestone is frequently encountered as an ingredient in mojo hands made by African-American hoodoo doctors, especially those for gamblers' luck and protection from evil. It is sometimes mentioned in old recipes for floor wash used by spiritualists to purify the home in the interest of keeping out evil spirits.
Copper sulfate has had widespread use over the years to control roots in sewer lines. Although most plants need a small amount of copper to survive, a high concentration of the metal can injure the roots without actually killing the plants. Introducing copper sulfate into the sewer line is an effective and easy way to increase the concentration of copper in the sewer water and kill the roots. The usual method is to pour 1 or 2 lbs. of crystals into the toilet nearest the sewer line, then flush the toilet.

Medical and Home Remedies:

A Cure for Warts - Said to be a Modoc Indian remedy. Soak the Bluestone rock, or crystals, in water, then use a toothpick apply it to a wart.
Toothache Relief - Place a tiny amount on a cotton tip and place it on the cavity for 4 seconds, then rinse your mouth thoroughly. (Said to Kill the Nerve)
Athletes Foot or Tinea - Add a teaspoon of bluestone to a basin or bucket of warm water and soak your feet for around 10 minutes. May sting a bit initially, but will kill the fungi. (Copper Sulphate is very corrosive so it should not be used in metal foot baths).
Toenail Fungus - Use a tablespoon of copper sulfate in a bucket of water to treat toenail fungus. Soak the toenails for 10 minutes a day for 7 days in the solution.
Canker Sores - Copper sulfate is an old remedy for canker sores that goes back at least to the 19th century. It is an astringent, and was also known as "lunar caustic." It stings upon application, but the canker sores should be gone in a day or two.

This image shows a mound of vivid, sparkling blue copper sulfate crystals sits on a pale marble-like surface, with small granules scattered around the base. Behind the crystals is a cream-colored sign bordered in black that clearly labels the substance as Copper Sulfate (Bluestone) and includes the chemical formula CuSO4 5H2O along with the scientific name Copper(II) Sulfate Pentahydrate. The lighting highlights the crystals' glassy texture and intense electric-blue color, creating a clean, educational laboratory-style presentation against a soft neutral background. Image © Disabled World.

Know of a Bluestone "Cure"?

1 - My doctor gave me a bit of bluestone (copper sulphate) to gently rub onto the proud flesh of my little finger after I had squashed it in a door. It had, of course, begun to heal before that. I rubbed the stone on the proud flesh quite vigorously and often, and told him that he hadn't informed me how much it would hurt. He said "I was afraid if I told you it would hurt you might not use it." The treatment worked fine and quite quickly. I am using it again for the same reason after knocking that same finger with an axe - Submitted by Wolfe

2 - My mother related the following information from her childhood. In the early 1900's, my grandmother used Bluestone to treat poison ivy reactions. Bluestone was expensive (for a farm family) and was stocked by the local general store. No one was allowed to touch the Bluestone except Grandmother. She was concerned it may be poison. The application method was to dip the Bluestone in water. The damp stone was gently rubbed over the area, applying blue liquid. It burned a little but provided relief from the horrible itching. Only one application was required - Submitted by Mary J.

3 - Olive G. from Australia was kind enougth to send us her story on "Blustone" usage. Here is her story in her own words... I live in Australia and I will be 74 years old in May. A couple of weeks ago I tripped and fell, wounding my left knee. The open wound was extremely painful and began to fester. I had difficulty walking and sleeping. This brought back memories of an earlier time in my new life, when I suffered a similar open knee wound as a child in India.

4 - I was born in India where I lived until the age of 16. At the age of around 9, I fell on a gravel surface and wounded my right knee, which refused to heal and left me incapacitated. The wound began to fester and increased in size - the pain was unbearable and I became very sick with high fevers and weight loss. I missed 9 months of schooling and the usual fun and activities enjoyed at that age in a railway colony in India at the time. All the prescribed medication, available in those days, was tried and failed. Soon, I was at death's door. Finally, my worried father was advised that amputation of the leg was the only way to save my life.

Understandably, my father was reluctant and kept putting off what seemed to be the inevitable. During this time, a resident, who was a member of the close knit colony community, approached my father and offered him a powder which, he explained, had been very effective in the cure of his mother's broken leg. Desperate to save my leg from amputation, my father would have tried just about anything and decided to 'take a chance'. The wound was cleaned and dried and the powder applied, at which point, I learned later, I screamed and passed out. My father was horrified and believed he had killed me. It was decided not to repeat the treatment again, as it was just too dangerous. A week later, a scab had formed and the pain had eased. At this time, the colony doctor came to check on me and was astonished at the sudden improvement. My father told him about the powder and fetched it for his examination. On looking at the powder, the doctor gasped. He told my father it was Bluestone, usually used on horse wounds, and that he was surprised it hadn't killed me!!!!

Thanks to Bluestone, I didn't lose my leg, but I still have the scar and memories of that awful period in my childhood. My recent wound made me curious about Bluestone and prompted me to check it out on the internet. It made fascinating reading - Submitted by Olive G.

5 - Bluestone for mouth ulcer(s): Heat the bluestone in a pan until it changes to a brown-blue color. Mix with some water and apply it to the ulcer. "In North India we use it for this purpose. I tried it many times and each time it worked. It can cure ulcer in a single day" - Dinesh Kumar.

Do you know of any other "Grandmother" home cures using Bluestone? If so you can contact us so we can add to the list.

IMPORTANT WARNINGS and PRECAUTIONS!

Chronic exposure to low levels of copper can lead to anemia
Vineyard sprayers experienced liver disease after 3 to 15 years of exposure to copper sulfate solution in Bordeaux mixture.
The warning signal "DANGER" must appear on the labels of all copper sulfate end-products containing 99% active ingredient in crystalline form.
Boots, protective gloves, and goggles should be worn by anyone handling this material. Skin should be washed immediately if contaminated, and work clothing should be changed daily if it is reasonably likely that it is contaminated with copper sulfate.
Copper sulfate is an irritant. The usual routes by which humans can receive toxic exposure to copper sulfate are through eye or skin contact, as well as by inhaling powders and dusts. Skin contact may result in itching or eczema. Eye contact with copper sulfate can cause conjunctivitis, inflammation of the eyelid lining, ulceration, and clouding of the cornea.
Copper sulfate is classified for shipping purposes as a hazardous substance or hazardous waste. It may pose unreasonable risk to health, safety, or property, when transported. Copper sulfate is highly corrosive to plain steel, iron and galvanized pipes. It should not be stored in metal containers.
Burning copper sulfate may produce irritating or poisonous gases, and pollution may be caused by runoff from fire control or dilution water.
Copper sulfate is a strong irritant. There have been reports of human suicide resulting from the ingestion of gram quantities of this material. Some of the signs of poisoning include a metallic taste in the mouth, burning pain in the chest and abdomen, intense nausea, vomiting, diarrhea, headache, sweating, shock, discontinued urination leading to yellowing of the skin. Injury to the brain, liver, kidneys and stomach and intestinal linings may also occur in copper sulfate poisoning.
Copper sulfate can be corrosive to the skin and eyes. It is readily absorbed through the skin and can produce a burning pain, along with the same severe symptoms of poisoning from ingestion. Skin contact may result in itching or eczema. Eye contact with this material can cause: conjunctivitis, inflammation of the eyelid lining, excess fluid buildup in the eyelid; cornea tissue deterioration due to breaks, or ulceration, in the eye's mucous membrane; and clouding of the cornea.
Copper sulfate is very toxic to fish. Copper sulfate is toxic to aquatic invertebrates, such as crab, shrimp and oysters.
Bees are endangered by strong, water-based copper compounds, such as a Bordeaux mixture of copper sulphate, lime and water.
Copper sulfate and similar fungicides have been poisonous to sheep and chickens on farms at normal application rates.
Most animal life in soil, including large earthworms, have been eliminated by the extensive use of copper-containing fungicides in orchards.
Upon oral exposure, copper sulfate is moderately toxic. According to studies, the lowest dose of copper sulfate that had a toxic impact on humans is 11 mg/kg. Because of its irritating effect on the gastrointestinal tract, vomiting is automatically triggered in case of the ingestion of copper sulfate. However, if copper sulfate is retained in the stomach, the symptoms can be severe. After 1 to 12 grams of copper sulfate are swallowed, such poisoning signs may occur as a metallic taste in the mouth, burning pain in the chest, nausea, diarrhea, vomiting, headache, discontinued urination, which leads to yellowing of the skin. In cases of copper sulfate poisoning, injury to the brain, stomach, liver, or kidneys may also occur.

Frequently Asked Questions

What should I do if someone swallows copper sulfate?

Call emergency services or Poison Control right away at 1-800-222-1222 in the United States. Do not try to make the person vomit unless a medical professional tells you to, and keep the product container so responders can see exactly what was swallowed.

Is copper sulfate harmful to dogs and cats?

Yes. Pets that lick crystals, treated water, or spilled powder can suffer vomiting, drooling, diarrhea, and in serious cases liver or kidney damage. Contact a veterinarian or an animal poison control line immediately if you suspect exposure.

Why does blue copper sulfate turn white when it is heated?

Heating drives off the water molecules locked inside the crystals, leaving white anhydrous copper sulfate. Adding water back restores the blue color, which is why the reaction is often used as a simple test for the presence of water.

Is copper sulfate allowed in organic gardening?

Copper sulfate is permitted for plant disease control under the USDA National Organic Program, but only with restrictions. Growers must use it in a way that limits copper buildup in the soil, and repeated heavy use is discouraged.

Can copper sulfate be used to treat algae in a backyard pond with fish?

It is risky because copper sulfate is highly toxic to fish, especially in soft or acidic water. Treating the whole pond at once can also cause a sudden oxygen drop as dead algae decay, so many pond owners choose fish-safe algae products instead.

Can copper sulfate stain a swimming pool?

Yes. Too much copper in pool water can leave blue-green stains on plaster and light surfaces and can tint blond or light-colored hair green. Regular water testing helps keep copper levels within a safe range.

How should copper sulfate be stored and disposed of?

Keep it in its original labeled plastic or glass container in a cool, dry, locked area away from children, pets, and food. Never pour leftovers into storm drains, streams, or ponds, and check with your local hazardous waste program for proper disposal.

Are there safer alternatives to bluestone for warts and toenail fungus?

Over-the-counter salicylic acid products and freezing treatments are common options for warts, while topical antifungals such as terbinafine or clotrimazole are used for fungal infections. A doctor or podiatrist can prescribe stronger treatments when these do not work.

Insights, Analysis, and Developments

Editorial Note: Copper sulfate has one of the longer and more varied histories of any common chemical compound - stretching from ancient folk cures to modern agriculture and industrial electroplating. What makes this article worth reading carefully is not the novelty of the remedies it describes, but the clear and repeated caution woven through them: these are historical uses, many of them dangerous, and several that were once considered treatments are now understood to be toxic risks. For anyone curious about the origins of home remedies or the chemistry behind everyday agricultural products, this is a grounded and honest look at a substance that has been both genuinely useful and genuinely harmful throughout its long history.

Ian C. Langtree Author Credentials: Ian is the founder and Editor-in-Chief of Disabled World, a leading resource for news and information on disability issues. With a global perspective shaped by years of travel and lived experience, Ian is a committed proponent of the Social Model of Disability, a transformative framework developed by disabled activists in the 1970s that emphasizes dismantling societal barriers rather than focusing solely on individual impairments. His work reflects a deep commitment to disability rights, accessibility, and social inclusion. To learn more about Ian's background, expertise, and accomplishments, visit his full biography.