The common cold is a widespread viral infection affecting the upper respiratory tract, typically involving the nose, throat, and sinuses. While generally harmless, a cold can cause significant discomfort, prompting many to seek relief through over-the-counter medications.
Understanding the Common Cold
The common cold is primarily caused by viruses, with rhinoviruses being the most frequent culprits. These viruses enter the body through the mouth, eyes, or nose, often spreading via airborne droplets or direct contact. Once inside, they attach to cells in the nasal passages and sinuses, replicating and triggering an immune response.
Cold symptoms like runny nose, stuffy nose, sneezing, sore throat, cough, mild body aches, and headache are largely a result of the body’s immune system fighting the infection. For instance, the immune response releases chemical messengers called cytokines, which widen blood vessels and accumulate fluid, leading to congestion and a runny nose. Because colds are viral, antibiotics are ineffective.
Targeting Cold Symptoms: How Medicines Work
Over-the-counter cold medicines do not cure the viral infection but rather target specific symptoms to provide relief. These medications contain various active ingredients, each designed to address a particular discomfort associated with the common cold.
Decongestants
Decongestants, such as pseudoephedrine and phenylephrine, relieve nasal stuffiness and pressure. They act as alpha-adrenergic agonists, stimulating receptors in the blood vessels lining the nasal passages. This stimulation constricts blood vessels, reducing swelling and inflammation in nasal tissues. This decreases mucus production and allows for easier breathing.
Pain Relievers and Fever Reducers
Medications like acetaminophen, ibuprofen, and naproxen alleviate pain and reduce fever. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen block cyclooxygenase (COX) enzymes. These enzymes produce prostaglandins, chemicals that contribute to inflammation, pain, and fever. By inhibiting prostaglandin production, NSAIDs reduce these symptoms.
Acetaminophen, while not an NSAID, also reduces pain and fever. Its exact mechanism is still being researched, but it is believed to work primarily in the central nervous system. It may also inhibit COX enzymes, but its effects are thought to be more localized to the brain, helping to reset the body’s temperature regulation and raise the pain threshold.
Cough Suppressants (Antitussives)
Cough suppressants, such as dextromethorphan, calm the cough reflex. Dextromethorphan affects the part of the brain responsible for controlling coughing. It disrupts communication between the brain and nerves that provoke coughing, reducing the urge to cough and providing temporary relief from a persistent cough.
Expectorants
Guaifenesin is a common expectorant that helps thin and loosen mucus in the airways. It works by stimulating respiratory tract fluid production. This increases the volume and decreases the viscosity of respiratory secretions, making the mucus less sticky and easier to cough up. Thinning the mucus allows cilia, tiny hair-like structures in the airways, to more effectively move the loosened secretions out of the respiratory tract.
Antihistamines
First-generation antihistamines, such as diphenhydramine and chlorpheniramine, are included in some cold formulations. These medications block histamine, a chemical released by the body during an immune response. Histamine contributes to symptoms like sneezing, runny nose, and watery eyes. First-generation antihistamines cross the blood-brain barrier and can cause drowsiness, which may also help with sleep when cold symptoms are disruptive. They also help dry up nasal secretions, reducing a runny nose.
Important Considerations for Safe Use
Using cold medicines safely requires careful attention to product labels. Always read the directions to determine the correct dosage and how often to take the medication. Taking more than the recommended amount can lead to serious side effects or overdose.
Select medicines that specifically target your symptoms to avoid unnecessary ingredients. Many multi-symptom cold products contain several active ingredients; be cautious to avoid “double-dosing” by taking multiple products that contain the same ingredient, such as acetaminophen. Overdosing on acetaminophen, for example, can cause liver damage. Be aware of potential side effects, which vary by ingredient, and consult a healthcare provider if symptoms worsen, do not improve, or if new, severe symptoms appear.