Being a fungus does it have negative effects similar to that of mold, especially on the respiratory system?


2 Answers 2


This is not my area of expertise but Usnea appears to be a fairly well-known phytomedicine (Prateeksha et al. 2016).

However, the US Food and Drug Administration (FDA) had received a number of reports of liver toxicity related to the ingestion of dietary supplements that contain usnic acid derived from Usnea (Lei Guo et al. 2008). Upon this, usnic acid and Usnea barbata lichen were analysed by the National Toxicology Program (NTP) for their toxicity.

The report issued as a nomination background does not mention any known negative impacts on the respiratory system.


According to the Institute for Traditional Medicine and the Gale Encyclopedia of Alternative Medicine:

  • Usnea (aka Songluo or "Old Man's Beard") is a fruiticose lichen (a type of symbiosis containing a fungus).

  • Used in traditional medicine worldwide, including historically in China, Europe and by native Americans, as well as globally today.

    • "Uses": topical antiseptic; therapuetic agent; medicinal herb; anti-cancer

    • It has traditionally been used in the treatment of bronchitis, in the treatment of tuberculosis, to ease coughing, to cleanse lungs and as an expectorant (i.e, to resolve phlegm).

      • Contains a secondary metabolite, usnic acid, which is claimed to be an effective inhibitor of gram positive bacteria-including tuberculosis, staphylococcus, streptococcus, and pneumococcus

So Usnea is often used for the lungs. In fact, today, supporters of traditional medicine still use it rather regularly as an expectorant. I could find no sources that claimed that this was unsafe or had any negative effects on the respiratory system. I would think that if you were to inhale any usnea, its effects would simply rid your body of any particulates during expectoration.

  • However, a number of sources (e.g., see Sanchez et al., 2006, here , here and here) mention that usneic acid can cause liver damage (and failure).

Disclaimer: I did not find any reputable source acknowledging usnea to be effective at treating any of the aforementioned ailments. Use at your own risk.


  • Sanchez, W.T., Maple, T.J., Burgart, L.J. & Kamath, P.S. (2006). Usnic acidhepatotoxicity. Mayo Clinic Proceedings 81: 541-544
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    $\begingroup$ Yes you're right that a lichen is a symbiosis of fungi and algae (or other photosynthesizing organisms such as cyanobacteria). But simply calling a lichen a fungus is like calling salt water salt. $\endgroup$ Commented Feb 28, 2017 at 14:49
  • $\begingroup$ To my knowledge a lichen is a fungus and an alga living in a symbiotic relationship. The answer is A+, thanks a lot $\endgroup$
    – user30163
    Commented Feb 28, 2017 at 14:52
  • $\begingroup$ First off I accidentally deleted my first comment. It is this relationship that made me wonder if it is harmful in the first place. $\endgroup$
    – user30163
    Commented Feb 28, 2017 at 14:57
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    $\begingroup$ I think the fact whether it can be used therapeutically doesn't mean it won't do harm. Also, while a bit of drug X (say digitalis extract) may be beneficial, a lot of it may kill you. So from a toxicological vantage point things are never either good or bad. $\endgroup$
    – AliceD
    Commented Feb 28, 2017 at 15:09
  • $\begingroup$ @AliceD Right. And just because I did not find any sources discussing "dangers" of using usnea, does not mean that none could exist. In fact, it could be that the expectoration I mentioned is due to irritation from the usnea and that long-term use could cause damage. Again, I found no sources discussing this in detail. However, I would think that general or irregular use would probably not be too harmful since usnea has been used for so long without any acknowledged negative impacts on the respiratory system. But as I said: USE AT YOUR OWN RISK. $\endgroup$ Commented Feb 28, 2017 at 15:17

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