Brief Answer:
Please see the answer.

Detailed Answer:
Hi,thank you for posting your query on HealthcareMagic,
The cause of coughing up clear mucus might be as follows:

Common Cold and Influenza:
You may produce clear mucus if you have influenza or are suffering from the common cold. These viral infections will make excess mucus accumulate at the back of your throat. You will notice clear and thin phlegm during the first few days of your illness, but it becomes yellow when your immune system takes charge of things. The phlegm will turn clear again when your immune system is about to eliminate the infection.
You may get relief by taking medicines like saline nasal sprays ,Mucolytic like Ambroxol.
Also avoid cold food.Do steam inhalation.Drink lots of warm fluids.

Bronchitis(Inflammation of Airway).
It might be due to viral infection/Allergy/exposure to dust,etc.
Same as cold,You may get relief by taking medicines like saline nasal sprays and Mucolytic like Ambroxol.
Also avoid cold food.Do steam inhalation.Drink lots of warm fluids.
Install a humidifier in your home to add moisture to dry air.

Allergy-
Exposure to certain Air-born particles like dust,pollens,or certain food items can cause allergy leaing to excessive buildup of clear mucus.
In such a case,avoid allergy triggers (like dust )and exposure to allergens.
You can take medicine like Oral Antihistaminic like Cetrizine.

Gastroesophageal Reflux Disease (GERD):
It is also a common cause .Acid reflux will irritate the airway leading to clear mucus.
In such a case,you may find relief by taking medicines like Pantoprazole and Antacid like Liquid Digene.
Take steps to avoid heartburn triggers, such as peppermint, onions, caffeinated beverages, chocolate, tomatoes, citrus juices, and spicy foods. You should also avoid overeating and never go to your bed with a full stomach. Be sure to eat slowly, quit smoking, say no to alcohol, and wear loose-fitting clothes to ease symptoms of GERD.

Hope this answers your question.I would be happy to answer if you have any follow-up questions.Take care.

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