Is there an otc medicine which is safe to take while breastfeeding that will alleviate sinus congestion?

May decrease milk: While it is safe to take otc medication, just like it can dry up the mucous in your nose, it can dry up your milk production as well. I recommend local/topical treatment like a nasal spray such as afrin, humidity, nasal saline drops, or warm/steamy beverages such as teas. Also make sure to get plenty of fluids yourself - both to keep mucous thin and ensure your milk supply.