Post-nasal drip is the accumulation of mucus in the back of the throat, which can cause a feeling of congestion, a sore throat, or a cough. Treatment for post-nasal drip usually depends on what might be causing it. Here are some ways to stop post-nasal drip:

1. Stay hydrated: Drinking more fluids, preferably water, can help thin out the mucus.
2. Use a humidifier: A humidifier can add moisture to the air and help thin out the mucus.
3. Elevate your head: Propping yourself up with extra pillows when you sleep can keep mucus from collecting in the back of your throat.
4. Saline nasal sprays: Saline nasal sprays moisturize your nasal passages, making it easier for mucus to drain.
5. Gargle with saltwater: Gargling with salty water 3 or 4 times a day can help relieve post-nasal drip.
6. Avoid irritants: Avoiding irritants such as cigarette smoke can relieve your symptoms.
7. Antihistamines and decongestants: Antihistamines and decongestants can often help with post-nasal drip caused by sinusitis and viral infections. They can also be effective, along with steroid nasal sprays, for post-nasal drip caused by allergies.

Its important to keep in mind that green or yellow mucus is not proof of a bacterial infection. Colds can also turn the mucus these colors, and they are caused by viruses, which dont respond to antibiotics. If symptoms persist, its best to consult a healthcare provider to determine the underlying cause of post-nasal drip and the best course of treatment.