Histamine may also have a role in causing coughs, but this is less certain.
Attachment to this receptor is necessary for histamine activity to occur.
(20) The first generation antihistamines also block the activity of a part of the nervous system, the parasympathetic system, that stimulates mucus glands secretion.
Decongestants may be taken by mouth or applied directly on the nasal mucus membrane in the form of nose drops and sprays.
(31) Decongestant nose drops and sprays have rapid and powerful action in relieving nasal obstruction.
Decongestants taken by mouth have less powerful and immediate activity but cause less problem with the cycles of recurrent nasal obstruction than topical preparations.