don't know if this is helpful or not, but weed is a bronchial dialator. this means, unlike cigarettes which cause the tissue in your throat to contract, weed will actually open you up a bit. i find when i'm sick and coughing a lot that smoking a little weed relaxes the muscles in my throat and helps me breathe better. of course, this also probably has to do with the fact that i'm a hopeless pothead. as for congestion, i'm not really sure, but i suspect that, if anything, it would reduce congestion. try exhaling some hits through your nose and see what happens.
--ade
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I am a drug. Take me.
--Salvador Dali