Dettol (like any ordinary household cleaning product) is actually poisonous... It is a chemical after all.  I am glad that you have rid yourself of the smell of vomit, however be sure that your car is adequately ventilated if you still have the strong smell of dettol, it can be an irritant if inhaled, which is why people are supposed to wear gloves, safety glasses and protective clothing if handling bulk quantities. 

A more natural alternative is to wipe away any excess chunks, (doesn't that paint a pretty picture) and sponge with water, then apply baking soda, (this will help soak up the fluid) and vinegar which will react with the baking soda and clean it off. I am not much of an expert, however I do try to use natural alternatives and earth friendly products when possible.  You might find these groups interesting to check out: www.minti.com/groups/270/Natural-Living/ & www.minti.com/groups/49489/Saving-the-planet/.

Excellent tip there is nothing worse then travelling and you have a few 100 klms to go and that smell is in the car.