Sandalwood is considered extremely cool, which is the reason behind people putting sandalwood paste on their foreheads.

The scientific reason behind placing sandalwood on the mouth of deceased is that it tones down the unbearable and intense smell of burning flesh and bones during cremation.  

http://daily.bhaskar.com/article/JM-why-sandalwood-is-placed-on-the-mouth-of-the-deceased-4151304-PHO.html?seq=2