It is not unusual for cough to persist for weeks, or for even several months, after a cold or other respiratory infection. This is particularly true for people with a history of asthma or chronic bronchitis. The "white, foamy" material you are coughing up might be unrelated to your cold. For that reason and because you could have had pneumonia with your cold, you should return to your doctor and probably have a chest x-ray taken.
Codeine-containing cough syrups or a medicine called amitriptyline can often give relief of a cold-related cough.
Re my post above concerning saliva infection - I have a very foul metallic taste in my mouth all the time and a very foul breath.
I have had a white foamy saliva infection that also desensitizes my tongue and taste buds. I have taken 2 cycles of Amoxicilan and it gets better about the 4th day of medication - then returns after meds are finished. Occassionally, after eating (especially carbohydrates) I find small white parasites(?) attached to my gums and they do not come off with a tooth brush - I must extricate them. There seems to be a feeding frenzy in my mouth following meals. This all started with an ear infection in July which was promptly cleared - then the feeling of clogging in my throat and the foamy saliva. I am an American living in Italy and have not been able to find a doctor here who would do anything but prescribe Amoxicilan. PLEASE GIVE ME ANY INFORMATION THAT MIGHT HELP ME!
I HAVE DONE THAT, I HAVE HAD TWO CHEST X-RAY, THAT COUGH MEDICINE AND THAT WORKED TO TWO WEEKS AN DNOW I'M BACK COUGHING AND VOMATING ,,,,HELP