The Nose Knows
A "stuffy" nose, often the most irritating symptom of the common cold, is caused by inflammation of the blood vessels, which restricts airflow in the nose. "This may in fact be an attempt by the body's immune system to raise temperature within the nose, creating a hostile environment which may affect how successfully the viruses can replicate," says Professor Ron Eccles, founder and Director of the Common Cold Centre, Cardiff University. Mucus in the nose and airway is the first line of defense against infection. Nose secretions might also change in color when an individual has a cold, with the color intensity increasing as the cold progresses due to the volume and increased activity of immune defense cells and proteins.1
Virus Infecting the Throat
Cough: Another Bothersome Symptom
The cough exists to ensure the sterile environment of the lungs. Colds induce coughing by causing inflammation around the nerve endings in the throat and airways.
This causes a hypersensitivity of the normal cough reflex.1 A cough can be productive ("wet") or nonproductive ("dry").
A productive cough expels secretions from the lower respiratory tract that, if retained, could impair ventilation and the lungs' ability to resist infection.
A nonproductive cough is typically stimulated by a mechanical irritant or other type of irritant and serves no useful physiological purpose.2
The Surprisingly Mighty Sneeze
Sneezing is a protective reflex that occurs when foreign matter or external stimulants reach the nasal mucosa. This triggers the release of histamines, which irritate
the nerve cells in the nose, resulting in signals being sent to the brain through the trigeminal nerve network. The efferent pathways activate nasal glands, facial muscles,
and respiratory muscles, resulting in a powerful release of air (the velocity of air discharge can range up to 100 meters per second). Often, other protective reflexes
such as tearing and closing of the eyes occur in order to protect the nose and eyes from irritants.3,4,5
The Source of Your Symptoms
Cold viruses attack the upper respiratory tract, but they sometimes can also infect the bronchial tubes, the eyes, and the middle ear. Cold symptoms are not triggered by the viruses
themselves, but by the defensive reaction of the body's immune system. The body deploys immune cells and antibodies to destroy the invading virus. Unfortunately, in
most instances these reactions are an overreaction to the common cold virus—making you feel much more miserable than you need to feel.
- Your runny nose might be due to your body trying to quickly move fluids containing antiviral particles to the site of infection and flushing away the virus and damaged respiratory tract cells.6
- Your stuffy nose might be a result of inflammation caused by release of immune system messenger proteins called bradykinins.1
- Your scratchy throat might be due to localized inflammation also caused by these immune system messenger proteins.1
1 Eccles, R, Understanding the symptoms of the common cold and influenza, Lancet Infect Dis, 2005; 5: 718-725.
2 American Pharmacists Association, Nurse Practitioner Healthcare Foundation, American Academy of Physician Assistants. OTC Advisor: Advancing Patient Self-Care; Self Care for Fever, Cough, Cold, and Allergy, 2007.
3 Muether, P. S., et al, Variant Effect of First- and Second-Generation Antihistamines as Clues to Their Mechanism of Action on the Sneeze Reflex in the Common Cold, Clinical Infectious Diseases, 2001; 33.
4 King, et al, Clearance of mucus by simulated cough, Journal of Applied Physiology, 1985; 58(6): 1776-1782.
5 Quraishi, MS, et al, The rheology of nasal mucus: A Review, Clinical Otolaryngology, 1998; 23: 403-413.
6 Cate, TR, Rossen, RD, Douglas, RG, Butler, WT, Couch, RB, The Role of Nasal Secretion and Serum Antibody in the Rhinovirus Common Cold, American Journal of Epidemiology, 1966; 84(2).
