Psoriasis patients should be careful of flammable skin creams

[D Foster]

By the way.... how inflammable is coal tar?  The coal tar treatment thread

That would depend on the percentage used. 

Yes I think that you would have to evaporate the tar to create fumes before you could set it on fire. Fuel Oil is the same  in fact any type of flammable liquid you have to create a gas by atomising it or evaporation before you can set it on fire.

or you could put a wick in it 

Which would evaporate the tar therefore creating a gas.