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