By Dr. Mercola
The common cold is likely the most easily recognized illness. Symptoms include a runny nose, sore throat, itchy eyes and low-grade fever. The illness is usually mild, lasting one to two weeks and requires nothing more than supportive care at home. However, while mild, it often results in days of lost work, lost productivity and lost income.
The common cold is the leading cause of doctor visits, and American school children miss about 22 million school days each year due to colds. Some estimates are that 1 billion colds occur each year in the U.S.1 Children may have between six and 10 colds each year and the average adult suffers between two and four each year.
In the U.S. the majority of colds appear to occur during the fall and winter months. In the past, seasonal variations have been attributed to staying indoors during cold weather, lower vitamin D levels from lack of sunshine and close quarters with others who may be ill.
Growing up, your mom may have told you to stay warm and out of the cold to stay healthy. You may have dismissed this advice as an old wives' tale, as colds are caused by viruses and not by the weather. However, recent research has demonstrated that while viruses trigger your symptoms, cold weather has a significant impact on whether you "catch" a cold.2
How a Cold Starts
A cold passes through direct physical contact with one of nearly 200 viruses that can trigger symptoms.3 Someone who has a cold can pass it to you by touching your hand, sneezing near your face, or through contact with their body where the cold virus has been sprayed after a cough or sneeze. You may also acquire the virus after touching a door handle, computer keyboard or utensil where the cold virus has been deposited, and then touching your face or nose.
Once inside, the virus attaches itself to the lining of your throat or nose, triggering your body's immune system to send white blood cells. If you've built antibodies to this virus in the past, the fight doesn't last long. However, if the virus is new, your body sends reinforcements to fight, inflaming your nose and throat. With so much of your body's resources aimed at fighting the cold, you are left feeling tired and miserable.
Dr. William Schaffner, chair of the department of preventive medicine at Vanderbilt University School of Medicine, points out that you may not even know you've been around someone who has been sick, saying:4
"You can catch a cold even when you cannot recall being around anyone with a cold. It's not really a mystery — people can excrete [exhale] the cold virus for at least 24 hours before they become sick. Thus, the person from whom we caught the cold was without any symptoms when [he] passed the virus on to us."
• Season: The cold virus is spread more easily during cold weather months when many spend hours indoors, placing you in close proximity to those who are ill. Dry air in the cold months may dry your mucous membranes, making the symptoms of a cold much worse.
• Age: The immune system in children younger than 6 is still developing and they have not yet developed resistance to many viruses. These factors increase their risk for developing a cold.
• Weakened immune system: While children's immune systems are developing, others may have compromised immune systems, or other chronic illnesses or nutritional deficiencies. Lack of sleep and psychological stressors are two common factors that may weaken your immune system.
• Smoking: In a study of 391 people intentionally exposed to one of five cold viruses, researchers found those who smoked had a far greater risk of developing a cold than nonsmokers, and had a greater risk of developing subsequent infections.7 They concluded smoking increased your susceptibility to developing a cold.
• Exposure: If you are in a situation where others are in close contact, such as a school, day care or airplane, your risk for developing a cold increases.
Cold Weather Closely Associated With Your Immune Function
Cold weather not only drives people indoors where exposure to those who are already ill increases, but the temperature may also increase your overall risk. Although the name implies temperature has something to do with an increased risk, researchers from Yale University only recently discovered cold temperature weakens your first line of immune defense in your nose.8
Using a rodent model, scientists modified a strain of rhinovirus to enable it to infect mice in order to demonstrate the increased number of people with colds in the winter weather had a biological component as well as a behavioral one.
Researchers built their model based on the knowledge that rhinoviruses, responsible for nearly 50 percent of all colds, replicate faster at lower temperatures. They then asked if previous research wasn't looking at the wrong side of the equation, and instead should attempt to determine if your ability to fight these growing invaders was at all compromised by temperature.
Led by immunobiologist Akiko Iwasaki, Ph.D., the team designed an experiment in which they were able to observe what happened to nasal cells when the rhinovirus attacked.9 When the tissue was exposed to rhinovirus at body temperature, the cells were able to effectively mobilize the immune system to kill the virus before the viral cells replicated. However, at lower temperatures, the cells managed only a weak defense that allowed the virus to replicate quickly and become established.
To test the theory that at colder temperatures the immune system responds slower than at body temperature, they analyzed the chain of proteins defending the cells and found when the genes responsible for making the proteins were shut off, the cells couldn't mount a defense, even at body temperature. The rhinovirus may have found a niche by invading the body through the nose where the air is often cooler than body temperature.
The results of the study from Yale University were confirmed by researchers from Sweden and Scotland when they collected over 20,000 nasal swabs over three years and compared the results against local weather data,10 finding you are much more likely to get sick when it's cold than during warmer weather.
Fever Plays a Vital Role in Supporting Your Immune System
Other viruses, such as the influenza virus, begin to replicate and grow further into your lungs, specializing where temperatures are higher than your nose. These viruses carry genetic material that help jam the early warning system your cells use to fight infections. Scientists have also discovered specific strains of rhinovirus can successfully replicate further into your lungs and have been linked to asthmatic attacks in children.11
These new findings further suggest that your body develops fever to boost the effectiveness of your immune system to fight bacterial and viral invaders. Iwasaki believes it will be important to explore how higher and lower body temperatures may affect your immune system and how you are able to fight infections.12 Researcher Elizabeth Repasky, Ph.D., from the department of immunology at Roswell Park Cancer Institute, commented on the necessity of rising temperatures as it relates to your health:13
"An increase in body temperature has been known since ancient times to be associated with infection and inflammation. Since a febrile response is highly conserved in nature (even so-called cold blooded animals move to warmer places when they become ill) it would seem important that we immunologists devote more attention to this interesting response."
A fever is a substantial difference from your normal temperature of 98.6 Fahrenheit (F), more than 1 degree higher or lower. Your body normally fluctuates between 97.6 F in the early morning hours and as high as 99.6 F in the late afternoon.14 Body temperature may also vary between those taken orally, under the armpit or rectally, as internal temperature in the rectum is usually higher than skin temperature taken under the tongue or armpit.
The presence of a fever helps support your immune system's fight against invaders or may be triggered by an environmental factor such as heat stroke, drug abuse or alcohol withdrawal. Although effective in helping the body fight infections, sometimes a fever may go too high.
Internal temperatures greater than 105 F threaten the integrity and function of proteins necessary for life.15 Thus, while it may be beneficial not to treat low-grade fevers, it is imperative you seek medical care when a fever climbs to 104 F, before it can reach lethal heat.
Vitamins C and D Help Prevent Colds by Supporting Your Immune System
Vitamins C and D are intimately involved in the functioning of your immune system. Thus, maintaining adequate levels of these vitamins may help prevent a cold and likely will help shorten your cold. Some health experts, such as Dr. Ronald Hunninghake, advocate using vitamin C for anything from a cold to supporting cancer treatments.
Research supports the use of vitamin C during a common cold to reduce the length of symptoms and regular supplementation, especially during cold season, consistently reduced the duration of your cold.16
People with higher blood levels of vitamin C also have a lower risk of death from all causes.17 Typically, the higher the dose you take the better the results during a cold. However, there are limitations when taking oral vitamin C, as it can cause loose bowels. You can get higher doses when using IV vitamin C or liposomal vitamin C. Personally, I use 3 to 4 grams of liposomal vitamin C every hour when I get sick, with great results.18
Kiwi fruits are exceptionally high in vitamin C, along with vitamin E, folate, polyphenols and carotenoids. Research19 published in the British Journal of Nutrition found that a kiwifruit-packed diet reduced the duration and severity of upper respiratory tract infections symptoms in older individuals. Other foods high in vitamin C include: citrus fruits, red bell peppers, broccoli, Brussels sprouts, butternut squash, papaya, sweet potatoes and tomatoes.
Suboptimal levels of vitamin D also increase your risk of developing symptoms.20 Vitamin D is actually a steroid hormone with powerful antimicrobial actions involved in producing 200 to 300 peptides in your body responsible for fighting bacteria, viruses and fungi. The evidence is clear that the closer your vitamin D levels are to optimal levels, the lower your risk of developing a cold or the flu.
In the largest nationally representative study, researchers measured blood levels of over 19,000 Americans and correlated these results with reports of cold and flu.21 They found those who had the lowest levels experienced the greatest number of colds and flu.
Your best source is sensible sun exposure. If this is not an option where you live, using an oral vitamin D3 supplement is advisable. Just remember that with high-dose vitamin D3 supplementation you need to take additional vitamin K2 — MK7 form —to protect your arteries.
Vitamin D has a number of other health benefits as well, including reducing your risk of chronic diseases such as cardiovascular disease, Type 2 diabetes, heart attack, stroke and cancer. Vitamin D may also play a role in macular degeneration,22 multiple sclerosis,23 colorectal cancer, inflammatory bowel disease24 and inflammatory rheumatic diseases.25
Other Natural Remedies That Can Help Prevent Colds or Hasten Recovery
Despite significant advancements in conventional Western medicine, there is little to offer in the care and treatment of the common cold caused by viruses. Although your physician may prescribe antibiotics for a cold, these have no impact on your symptoms as antibiotics work against bacteria and not viruses. Antibiotics are effective only if you develop a secondary bacterial infection after your immune system has been assaulted by a virus.
An uncomplicated cold may last between two days and two weeks, depending on your overall health, the specific virus involved and your use of natural strategies to help reduce the length of your symptoms. Over-the-counter remedies typically do not speed your recovery time; they only affect your symptoms for a short period. Many of these contain acetaminophen (Tylenol) or ibuprofen (Advil) that suppress your body's ability to produce antibodies to fight the virus.26 This may actually lengthen the course of your illness.
For a list of 17 natural remedies you may consider to prevent a cold or to shorten the length of symptoms, see my previous article, "Natural Cold Remedies: What Works, What Doesn't."