Unsupported: There’s no evidence that activated charcoal treats diarrhea or other gastrointestinal problems.
Misleading: Activated charcoal doesn’t work for all poisons. For instance, it doesn’t work for poisoning caused by alcohols, corrosive substances like acids, and metals like lead. Its effectiveness also greatly depends on how soon it’s administered after the ingestion of poison. Activated charcoal is ineffective if hours have passed after the poison was ingested.
FULL CLAIM: “Charcoal absorbs and neutralizes poisons”; “If ever I had a baby who had a bit of diarrhea, I’d give a bit of charcoal [...] when I got a black nappy, I knew that my baby was well”
REVIEW
A Facebook reel posted in May 2024 claimed that “charcoal absorbs and neutralizes poisons”, drawing more than 1.3 million views to date. The claim was made by naturopath Barbara O’Neill, who has promoted unsubstantiated and potentially harmful health claims. Science Feedback debunked some of O’Neill’s claims in earlier reviews.
In one instance, she discouraged cancer patients from using chemotherapy, a conventional cancer treatment, and promoted sodium bicarbonate (baking soda) instead. This and other findings in an investigation by the New South Wales Health Care Complaints Commission led O’Neill to be barred for life from providing health services in Australia. But this hasn’t prevented her from doing so abroad in the U.K. and in the U.S.
O’Neill’s claim that charcoal can be used to treat diarrhea, even in infants, isn’t substantiated by evidence. The U.S. National Center for Complementary and Integrative Health states that “No solid evidence supports claims that activated charcoal helps with [traveler’s diarrhea], bloating, stomach cramps, or gas”. It also added that children shouldn’t be given charcoal.
However, O’Neill’s claim that “charcoal absorbs and neutralizes poisons” is somewhat accurate, although it exaggerates the effectiveness of charcoal and lacks important nuance. In fact, misunderstandings over activated charcoal’s effects have led it to be wrongly touted as a way to “detox”. We explain more below.
What is activated charcoal and how does it work?
The term “charcoal” may lead some users to believe that regular charcoal, like that used for barbecues, can also treat poisoning. But this is incorrect. Poison Control warns that people shouldn’t confuse burnt food and barbecue briquettes with activated charcoal; neither are effective to treat poisoning and “should never be used”.
Activated charcoal is a special form of carbon that’s been processed so it can effectively bind to other substances, a process known as adsorption. It’s made by heating carbon-rich material like coconut shells and peat at very high temperatures (600 to 900 degrees Celsius). The carbon is then “activated” using very hot gas, like steam or carbon dioxide. The hot gas erodes the internal surfaces of the charcoal, producing a highly porous substance with a very large surface area[1,2].
This review by toxicologist Kent Olson illustrates just how large the surface area of activated charcoal is. Given that typical activated carbon has an average surface area ranging from 800 to 1,200 square meters per gram, he calculated that “a 50-g dose of activated charcoal has an adsorptive surface area equivalent to about seven football fields”[2]. An American football field is roughly 5,230 square meters.
Activated charcoal is indeed used in emergency rooms to treat some cases of poisoning. It’s given orally or administered using an endotracheal tube if the patient is unconscious. When the charcoal comes into physical contact with the poison in the gastrointestinal tract, the charcoal adsorbs the poison. This reduces the amount of poison absorbed by the body and thereby reduces the poison’s effect on the body.
That said, activated charcoal cannot reverse the effects of poison that is already absorbed. A poisoned person should still seek medical attention even after taking activated charcoal. Poison Control states that “If a poisoning is serious enough to warrant the use of activated charcoal, the person should be monitored in an emergency room”.
Activated charcoal doesn’t work for all poisons and its effectiveness depends on multiple factors
Activated charcoal’s effectiveness depends on several factors, such as the amount of time that elapsed between ingestion of the poison and the administration of activated charcoal. Because the charcoal needs to come into physical contact with the poison, it isn’t useful if several hours have passed since the poison was swallowed, as the poison is likely to have been absorbed by the body already.
Another limitation is that activated charcoal doesn’t adsorb all substances equally well. In a previous review about activated charcoal, Olson told Science Feedback that ethanol, the main alcohol in alcoholic drinks, isn’t readily adsorbed by activated carbon.
The same goes for other forms of alcohol like methanol, states clinical guidance from the Royal Children’s Hospital in Melbourne, Australia. The guidance adds that activated charcoal doesn’t work well for corrosive substances, like acids and alkalis, or for metals like lead.
It’s also not helpful for cyanide poisoning. While activated charcoal does adsorb cyanide, a position paper by the American Academy of Clinical Toxicology (AACT) and the European Association of Poisons Centres and Clinical Toxicologists (EAPCCT) stated that “the rapid onset of life-threatening cyanide toxicity will obviate the usefulness of activated charcoal” in many cases[1].
Finally, while over-the-counter forms of activated charcoal exist, these aren’t as potent as those used in emergency rooms.
“The amount of charcoal in each activated charcoal tablet is relatively small (150 to 300 mg per tablet); to take a dose equivalent to what is commonly used in a hospital emergency department would require about 150 to 200 tablets,” Olson said.
There are few adverse effects associated with activated charcoal, making it relatively safe. However, there are still risks. For example, outside of a medical setting, activated charcoal can’t be given to an unconscious person or someone who is drowsy, as it can result in choking. Vomiting is also common and can lead to regurgitated stomach contents entering the lungs. Both of these can lead to respiratory complications like blocked airways and pneumonitis[1,2].
In his review, Olson highlighted the importance of “assessing each case individually” in determining the benefits and risks of administering activated charcoal for poisoning[2]. The AACT/EAPCCT position paper states that “[s]ingle-dose activated charcoal should not be administered routinely in the management of poisoned patients”[1].
REFERENCES
- 1 – Chyka et al. (2005) Position Paper: Single-Dose Activated Charcoal. Clinical Toxicology.
- 2 – Olson KR. (2010) Activated Charcoal for Acute Poisoning: One Toxicologist’s Journey. Journal of Medical Toxicology.
