# Safety & Hepatotoxicity
The main safety concern with usnic acid is liver risk.
### Why the warning exists
At higher doses, UA acts as a strong mitochondrial uncoupler.
That can drive:
* oxidative stress
* ATP depletion
* hepatocyte injury
* hepatocyte necrosis
### Important context
The most serious historical liver-injury cases came from high-dose weight-loss products rather than traditional lower-dose herbal use.
That context matters.
It does not make UA harmless, but it does explain why the worst cases cluster around a specific misuse pattern.
### Cancer-cell selectivity
Across several in vitro studies, UA appears more toxic to cancer cells than to non-cancerous cells.
That selectivity is one of its attractive features.
### Practical safety principles
* avoid casual high-dose use
* be careful with prolonged use
* prefer better-characterised formulations
* monitor liver function when dosing is meaningful
* review drug interactions properly
### Clinical takeaway
UA is not a soft, casual herb.
It is a potent compound with real upside and real risk.
### Key References
Toxicity of Usnic Acid: A Narrative Review\
NTP Technical Report on the Toxicity Studies of Usnea\
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