After an exposure to a cold or flu virus, the steps taken once infected will determine whether the symptoms will be mild and temporary, or one will become moderately to seriously ill for days or weeks. Sufficient intake of Vitamin A and Vitamin C every few hours along with taking additional remedies - as required depending on the severity of the viral infection - is most important when the first cold or flu symptoms (stuffy nose, sneezing, sore throat, cough, - or fever, headache, weakness, general aches and pains) are experienced.
Recommended doses for adults: Tablets or liver oil caps providing 5,000 IU of Vitamin A, several times a day. For children, ¼ adult dose (e.g. Cod liver oil caps provide 1,250 IU of Vit A + 400 IU of Vit D. Vitamin C dosages generally range from 500 - 1,000 mg for adults, and depending on age, up to ½ of adult doses for children. Ginseng, Cat's claw, and others can also be considered if warranted by symptoms. The goal is to control, and then resolve symptoms in less than 48 hours, supported by maintaining adequate fluid intake and rest. Thereafter, regular amounts of these or other daily supplements are resumed.
Trying to reduce any fever accompanying a viral infection is counterproductive and only prolongs the recovery time, however to avoid febrile seizures in younger children, their head should be kept cool when developing a high fever. Brain damage from a fever will generally not occur unless the fever is over 42 °C (107.6 °F).
Some sources advocate a high daily intake of Vitamin D to provide protection from viral infections, however a comparison of the rates or severity of "Upper Respiratory Tract Infections" between healthy adults with a very high intake (and high levels) of Vitamin D, and those with normal levels, fails to support these claims. Partly to blame is a strong Vitamin A / D antagonism, where too much of one will inhibit the effectiveness of the other, so an excessive Vitamin D intake can worsen mucus congestion.
While optimal Vitamin D levels (100-125 nmol/L / 40-50 ng/mL) help a normal - but not always a compromised immune system ward off colds and the flu, the symptoms of an acute viral infection improve faster following a temporary higher intake of Vitamin A, rather than a higher intake of Vitamin D.
Those with a weak, inefficient or overactive immune system frequently do not tolerate certain antiviral remedies that seem to work well for people whose immune system functions properly, with Echinacea being one example. However, while herbs such as Echinacea may be helpful for the Common Cold or Flu when used by individuals with a normal immune system, they tend to overstimulate the immune system even in healthy individuals as a result of cytokines - regulatory cell proteins such as lymphokines and interleukins - being ineffective against a Pandemic Virus. This is one reason why many younger, seemingly healthy individuals die during a pandemic flu.
Many compounds (e.g. Elderberry) also increase the production of immature White Blood Cells in individuals whose numbers are already on the high side, and thus worsen some forms of Leukemia. Various foods, spices, and beverages affect the immune system in a similar fashion, and should be increased or avoided accordingly:
* Sugar Alcohols (Xylitol, Sorbitol) are well tolerated by some individuals, but cause major gastrointestinal problems in others.
** Ca, Cr and Mg have anti-inflammatory properties. Adequate intake is important when fighting a viral or bacterial infection.
*** These may be helpful for a seasonal cold or flu with a normal immune system, but are contraindicated for a Pandemic Flu.
Items listed in the "Caution" column generally pose no problems for those with a healthy immune system, or some may actually improve their immune response. However depending on the amounts consumed, they are likely to cause a mucus-forming, or inflammatory response in individuals with a malfunctioning immune system. For instance, Probiotics help maintain a healthy gut, but they can be detrimental for individuals with a compromised immune system.
In addition to the above, the list of natural home remedies said to have antiviral properties include Aloe vera, Boneset, Buchu, Chamomile, Dragon's blood, Fenugreek, Goldenrod, Goldenseal, Honeysuckle, Juniper, Lysine, Lemon balm, Lomatium, Lonicera, Myrrh gum, Peppermint, Reishi, Schizandra, Shiitake, St. John's Wort, Thuja, Wild Indigo..., and the antiviral product COLD-FX, which contains an extract of Panax (quinquefolius) Ginseng.
The efficacy of these flu and cold remedies largely depends on someone's immune response to a particular virus and the particular remedy. For patients with an overactive immune system, or an excessive number of immature white blood cells, many of these herbal antiviral remedies actually worsen and prolong a bout with a seasonal cold, influenza, or a pandemic virus by overstimulating the immune system even more, instead of helping the body produce healthy and efficient white blood cells and thereby lowering their numbers and inhibit inflammation.
Or, a pandemic (H1N1 / H1N2 / H3N2 / H5N1...) virus is immune to cytokines such as TNF-a or IL-6, causing a cytokine storm as a result of the body trying to cope with its inability to fight the virus, which affects healthy individuals to their detriment as well. Remedies in the "Recommended" column are chosen to help reduce those problems. Several studies also found an apparent association between the seasonal influenza vaccine, and an up to 68% increased risk for infection with the H1N1 pandemic flu.
The immune system's recovery time from an intake of Simple Sugars listed in the "Not Recommended" column may take up to several hours for individuals with a normally-functioning immune system, but it may take several days or longer for someone with a weak, inefficient, or overactive immune system. This applies to "Simple Carbohydrates" only, but not to "Refined Carbohydrates" or "Complex Carbohydrates." See "Hypoglycemia" for details.
Honey is frequently recommended as an adjunct home remedy for those suffering from a viral infection. From clinical experience however - except for a local soothing effect - its use is more likely to delay a recovery for those with a weak immune system, rather than speed it up. If people consume honey or sugar-containing cough candy while fighting a cold or flu bug, a normal recovery it is likely despite - not because of their use.
In contrast to simple carbs (sugar, honey, fructose, molasses, syrup...), Sugar Alcohols such as Xylitol do not impair the immune system or worsen cold or flu symptoms. If they are tolerated and do not cause any gastrointestinal or other health problems, they can be substituted for other forms of simple sugars.