If you have allergies, nature is, unfortunately, not your friend. The pollen from trees, grasses, and weeds or indoor allergens like furry pets or dust can cause the inside of your nose to become swollen and, sometimes, itchy. When this happens, your body makes mucus to “trap” all those irritating allergens. Then, all that gooey mucus can keep coming out. Sometimes, if you’re less lucky, it wants to come out of your nose but--can't. So instead, it goes backward into your sinuses and/or your throat, causing sinus pain, headaches or a yucky cough and throat irritation.