Here's an MSDS for a brand of incense.
http://www.thegoodscentscompany.com/data/es1004051.html
"Most important hazard(s) : Xn - Harmful.
R 10 - Flammable.
R 20/21/22 -
Harmful by inhalation, in contact with skin and if swallowed.
R 36/37/38 - Irritating to eyes, respiratory system, and skin.
R 42/43 -
May cause sensitization by inhalation and skin contact.
S 02 - Keep out of the reach of children.
S 24/25 - Avoid contact with skin and eyes.
S 26 - In case of contact with eyes, rinse immediately with plenty of water and seek medical advice.
S 36/37/39 - Wear suitable clothing, gloves and eye/face protection"
I worked in the environmental cleanup field and have read a crapload of MSDS and actually wrote a few for our particular product. Bottom line, MSDS is a big CYA extravaganza. If there is ANY chance that ANYTHING could be caused by your product you MUST put it in the MSDS. We had an MSDS for a particular liquid that stated that it can cause permanent blindness within seconds of of exposure...and it totally could...at 100% concentration...which nobody uses...because it could cause permanent blindness in a matter of seconds!
That liquid was called Hydrogen Peroxide. You may recognize that as the brown bottles sold at drug stores as a disinfectant? Well in stronger concentrations, it's a powerful oxidizing agent that creates its own oxygen in fires and can eat away your flesh. Also, just for S&G, they put hydrochloric acid in there to keep it from venting oxygen during storage lol
Bottom line is you can't look at an MSDS and say that a particular chemical in a particular concentration is a health hazard especially if the HMIS number for human health is 0 or 1. If it's 3 or 4 though...keep the hell away!