Note: I am not in the medical profession. The following is not a recommendation. I write about it for information purposes only. It is best to check with a doctor before taking any medication.
It is pretty common to catch a cold when you're traveling, especially when you're sitting for hours on an airplane breathing recycled air - and germs. And although hopefully, you've packed carefully, including your first aid kit, you still might need some cold meds and you probably don't want to go searching when you've got a packed itinerary and the free time you do have you want to spend shopping and eating.
I had one of the worst colds I've ever experienced last fall when I went on my tea-trek out to Yunnan Province and the Linden Centre. The trip was still wonderful but I have a feeling my travel partners would have enjoyed it more if I hadn't been honking into tissues the entire time.
When I got back, a girlfriend introduced me to Ban Lan Gen Ke Li (板蓝根颗粒) medication that she gets over-the-counter in Chinese pharmacies. Since that cold, I take it religiously to fend off cold symptoms. I find it certainly does make the cold less severe and shorter.
Ban Lan Gen Ke Li is a Traditional Chinese Medicine that typically comes in little packets that you mix with hot water. You drink it like a tea. I don't mind the flavor - it reminds me of warm Coca-Cola. My local pharmacist recommends drinking it three times a day while your symptoms last.