Can nasal drip cause stomach problems?

Yes. Post-nasal drip from viruses, allergies, and bacterial sinusitis can go down the back of the throat and cause frequent throat clearing, cough, bad breath, and nausea when it goes into the stomach. Sometimes acid-reducers can help but the best approach is to target the drip with saline rinses, steroid sprays, and antihistamines. With continued symptoms, evaluation by an allergist or ENT can help.
May. Nasal drip can be accompanied by excessive post-nasal drainage of mucous. When this post nasal drip is copious it can cause nausea. In some severe cases it can cause some stomach discomfort due to the nausea and occasionally, even vomiting.