What are the reverse effects of kava?

October 9, 2025 •

3 min read

In the United States, kava is sold as an over-the-counter dietary supplement, but the Food and Drug Administration (FDA) has warned that its use is associated with a risk of severe liver injury. Before consuming this herbal remedy, it is vital to understand what are the reverse effects of kava.

Quick Summary

Kava (Piper methysticum) is an herbal supplement used for anxiety and relaxation. Its adverse effects range from mild dizziness to severe, potentially fatal liver damage, skin reactions, and neurological issues.

Key Points

Severe Liver Damage: The most significant reverse effect of kava is hepatotoxicity, which can lead to hepatitis, cirrhosis, and liver failure.
Neurological Impairment: Kava is a CNS depressant that can cause dizziness, drowsiness, and impaired motor function. Long-term use may lead to tremors and movement disorders.
Kava Dermopathy: Chronic, heavy kava consumption can cause a characteristic dry, scaly, yellowing skin rash that is typically reversible upon cessation.
Drug Interactions: Kava interacts dangerously with alcohol, benzodiazepines, acetaminophen, and many other drugs by affecting liver enzymes, increasing toxicity risks.
Regulatory Warnings: The FDA has issued a consumer advisory warning about the risk of severe liver injury from kava supplements, and it is banned in several countries.
Quality Concerns: The risk of toxicity may be influenced by the quality of the kava, including which parts of the plant are used and the extraction method.
Consult a Doctor: Due to the serious potential for adverse effects, it is crucial to speak with a healthcare provider before using any kava product.

What is Kava?

Kava (Piper methysticum) is a plant traditionally used in the South Pacific for social and ceremonial drinks, with kavalactones as its active compounds. In Western countries, kava supplements are used for their anti-anxiety and sedative effects. Despite some evidence for short-term anxiety relief, significant safety concerns, especially regarding its adverse effects, have led to restrictions or bans in several countries. The FDA in the U.S. has warned consumers about the potential for severe liver injury from kava products.

The Most Serious Reverse Effect: Liver Damage (Hepatotoxicity)

The most serious known adverse effect of kava is severe liver damage. Reports since the late 1990s detail numerous cases of kava-induced liver issues, including hepatitis, cirrhosis, and liver failure, sometimes requiring liver transplants.

Symptoms suggestive of liver injury include:

Jaundice (yellowing of skin and eyes)
Nausea and vomiting
Unusual tiredness
Dark urine
Abdominal pain

The exact cause of kava-related liver damage is still debated. Potential factors include:

Poor Quality Products: Using non-root parts of the plant or contamination with molds (aflatoxins) may contribute to toxicity. Traditional preparations differ significantly from some commercial extracts.
Metabolic Issues: Kavalactones can interfere with liver enzymes (cytochrome P450), affecting the metabolism of other substances and potentially causing toxic buildup.
Individual Susceptibility: Genetic factors might make some people more prone to kava's toxic effects.

Individuals with liver conditions, those who consume alcohol regularly, or those taking liver-affecting medications should avoid kava.

Neurological and Cognitive Effects

As a central nervous system depressant, kava can cause various neurological side effects, especially at higher doses.

Short-Term: Dizziness, drowsiness, headaches, and reduced coordination and reaction time are common. Operating vehicles or machinery after using kava is not recommended.
Long-Term: Chronic, heavy use has been linked to tremors, involuntary movements, ataxia, and potentially worsening Parkinson's disease symptoms.
Dependence: While not typically causing physical addiction, psychological dependence is possible, with some reports suggesting it can be habit-forming with potential tolerance and withdrawal.

Dermatological Reactions: Kava Dermopathy

A notable side effect of heavy, long-term kava use is kava dermopathy. This condition presents as a dry, scaly rash (ichthyosis), often with yellowish discoloration, on the palms, soles, face, and back. It is distinct from jaundice and usually resolves upon stopping kava within weeks or months.

Drug Interactions

Kava can interfere with liver enzymes, leading to dangerous interactions with many medications and other substances. Combining kava with certain drugs can increase sedative effects and the risk of liver damage.

Substances to avoid combining with kava include:

Alcohol: Greatly increases the risk of liver toxicity.
Sedatives (e.g., benzodiazepines): Can cause excessive drowsiness and disorientation.
Acetaminophen: May increase the risk of liver damage.
Antidepressants: Can lead to increased drowsiness or other additive effects.
Parkinson's Disease Medications: Kava might interfere with their effectiveness.
Medications processed by Cytochrome P450 enzymes: Kava can alter their metabolism, causing unpredictable effects.

Comparison of Kava with Other Anxiolytics


Feature	Kava	Benzodiazepines (e.g., Xanax, Valium)	SSRIs (e.g., Prozac, Zoloft)
Mechanism	Affects GABA, dopamine, and norepinephrine systems.	Enhances GABA's inhibitory effects.	Blocks serotonin reuptake.
Primary Use	Short-term anxiety, stress, insomnia.	Acute anxiety, panic attacks, seizures.	Generalized anxiety, depression.
Addiction Risk	Low physical, potential psychological.	High physical and psychological; withdrawal risk.	Low addiction; potential discontinuation syndrome.
Key Side Effects	Liver damage, skin rash, dizziness, GI upset.	Drowsiness, confusion, memory issues, dependence.	Nausea, insomnia, sexual dysfunction.
Regulatory Status	Supplement with FDA warnings; banned in some areas.	Prescription-only controlled substance.	Prescription-only medication.

Conclusion

While kava is used for relaxation, understanding what are the reverse effects of kava is essential. The potential for severe liver damage is a major concern, leading health authorities like the FDA to issue warnings. Other risks include neurological issues, kava dermopathy, and dangerous drug interactions. Given these serious risks, consulting a healthcare professional is crucial before using any kava product.

Authoritative Link: For more information, visit the National Center for Complementary and Integrative Health (NCCIH) page on Kava.

Frequently Asked Questions

The most serious side effect of kava is severe, potentially fatal liver damage (hepatotoxicity), which can include hepatitis, cirrhosis, and liver failure.

Yes, long-term, heavy use of kava can cause a specific skin condition called 'kava dermopathy,' which is a dry, scaly, and sometimes yellowish rash that is reversible after stopping kava intake.

No, it is not safe. Combining kava with alcohol significantly increases the risk of severe liver damage and can also enhance sedative effects.

Kava is not considered to be physically addictive in the same way as opioids or benzodiazepines. However, there is a risk of developing a psychological dependence on its calming effects, and some sources suggest it can be habit-forming.

Yes, kava can interact with many medications, including sedatives (like benzodiazepines), antidepressants, alcohol, and drugs metabolized by the liver (like acetaminophen). These interactions can be dangerous and increase the risk of toxicity.

Kava has been restricted or banned in countries like Canada, the UK, and Germany due to numerous reports linking its use to severe liver toxicity, including cases of liver failure.

Symptoms of liver problems from kava include nausea, unusual tiredness, dark urine, abdominal pain, loss of appetite, and jaundice (yellowing of the skin or eyes).