is caused due to broncho-constriction (obstruction of smaller airway passages) which is indicative of Hyper-responsiveness of air passages to an allergen.
Nebulisation will provide symptomatic relief by causing broncho-dilation (dilating the smaller airway passages, relieving the obstruction & increasing airflow to lungs)
And the presence of foul smelling sputum indicate lower respiratory tract
involvement such as Bronchiectasis
(a condition grouped under COPD, in which there is irreversible dilatation of the air passages due to damage to bronchial wall)
So...it will be better to consult a Pulmonologist
And make sure that you are well protected from cold, dust & other allergens.
Other than that eat a healthy diet, avoid stress
, get good sleep, think positive and stay happy.
Wishing you good health.
Thanks & take care.