Cold medicines typically contain a medication that can increase heart rate, among other things. It is my understanding that if our thyroid has been removed, those warnings no longer pertain to us. It might also be true that if you are well-controlled on antithyroid meds, you might be able to take them, too. BUT, talk with your doctor’s office first to double check — both my information and whether you need to be concerned.
In the interim (it is, after all, the weekend) using nose drops might help. I was also advised to take a product called Mucinex, which is essentially the main ingredient in Robitussin cough medicine in a pill form. It loosens up the congestion quite nicely, and I am unaware of warnings on the label that talk of thyroid condition. But check.