Hi welcome to the health care magic Thick mucus or phlegm can lead nausea feeling Whenever there is damage to respiratory epithelium or inflammation, cough production occurs as reflex mechanism and because of inflammatory mediators excess mucus production occurs Cause for phlegm should be ruled out like.... -Allergy inflammation -bronchitis -pneumonia (if fever, chest pain present) Investigations needed like CBC, Auscultation, chest x ray etc... If needed spirometry done for further work up (only if needed) If these presentation because of infection antibiotic course prescribed.. For excess wet cough expulsion Ambroxol containing syrup can be prescribed Hope your concern solved Consult physician or pulmonologoist for examination and discuss these information with him Take care