I started taking 600 mg of clindamycin every 8 hours yesterday for endometritis infection. I took 300 to start and 600 the second dose. I had no problem after the first dose. 1 hour after the second dose, phlegm started pooring down my throat and my nose became completely stuffed. 14 hours later, I am still stuffed and have some (much less) phlegm. I have not taken any more of the clindamycin. Is this an alergic reaction or just a side effect of the medicine?