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]