Alicia Drakiotes posted a brief note about the toxicity of cedar, and said
that she'd heard the acids in cedar cause irreversible damage to the central
nervous system.  Cedar can--but not always--cause damage, but to the lungs,
so it's almost entirely due to inhaled cedar.  I posted an extensive review
of the effects of cedar on our local ferret group's web page and I have read
some of the papers going back to the 1940s on this.  A lot of evidence
exists to show that long-term exposure to cedar can cause asthma, which is
irreversible *in HUMANS* roughly half of the time.  Cedar and its primary
irritant, plicatic acid, also have an effect on the immune system...mostly
in those aspects related to inflammatory response.  All of the evidence
suggests that this is in response to the inflammation in the lungs and
doesn't cause inflammatory reactions elsewhere in the body.  To my
knowledge, humans and animals exposed to cedar or plicatic acid do NOT
develop other inflammatory disorders such as inflammatory bowel syndrome,
any of the rheumatoid disorders, atopy, etc.  The effect of cedar seems to
be entirely limited to the lungs.  I never saw any evidence that plicatic
acid has any effect on the CNS.  It may not be able to cross the blood-brain
barrier.  It is, however, a potent respiratory irritant and chronic
high-level exposure can lead to asthma in *some* of those exposed.  It's
possible that a shampoo with cedar oil would be fine for humans as most
people don't go around stiffing other people's hair.  It might be best to
err on the side of caution for animals that sniff each other a lot or sleep
with each other with their noses burrowed in to the fur of their neighbors.
(Sound like any critters we know?)
 
   BTW, our local group's web page is at:
        http://doomsday.phy.duke.edu/ferrets/
   Follow the links to the cedar & pine review.
--Jeff Johnston ([log in to unmask])
[Posted in FML issue 1692]