Astragalus (Astragalus membranaceous) is a Chinese herb with powerful immune-strengthening properties. Scientific studies have shown that astragalus raises levels of immunoglobulin A and immunoglobulin G, both of which play important roles in fighting off cold and flu viruses. Astragalus also increases production of interferon, an immune compound that interferes with the ability of viruses to replicate.

Garlic (Allium sativum) has a long history of use for preventing respiratory illnesses. When taken regularly, garlic significantly decreases the incidence of viral infections. For optimal protection, eat one or two cloves of fresh garlic daily. For those who have difficulties eating raw garlic, standardized preparations or aged garlic extracts are an alternative. The regular use of garlic shouldn't be combined with blood-thinning drugs, such as Coumadin.

Siberian ginseng (Eleutherococcus senticosus) improves the ability of the body to cope with environmental stressors; it also enhances immunity. Taking the herb regularly strengthens energy, vitality and resistance to illness. Siberian ginseng is safe to take long term; it does not have the potential for overstimulation, as can happen with Panax ginseng.

Echinacea (Echinacea spp.) stimulates immune activity and strengthens cells against invading microorganisms. Studies have shown that if echinacea is taken at the first sign of symptoms, it can prevent the illness from developing. But even if symptoms are full-blown, echinacea can shorten the duration of the illness by up to four days. To fight off a cold or flu, stir 1/2 teaspoon of liquid extract into a glass of water and take every hour until symptoms subside.

Elderberry (Sambucus nigra) is traditionally used in Europe for treating influenza; compounds in the fruit disarm the flu virus, prevent it from replicating and strengthen cells against invasion by the virus. Studies have shown that taking elderberry extract at the first sign of a cold or flu cuts recovery time in half. Take 1 teaspoon of elderberry extract or 1 tablespoon of elderberry syrup four times a day until symptoms are relieved.

Chase chills
Hot ginger (Zingiber officinalis) tea loosens nasal congestion, eases a sore throat and relieves chills. Use ginger tea bags, or make fresh ginger tea by simmering 1 heaping tablespoon of fresh grated ginger root in 2 cups of water in a covered pot for 10 minutes. Strain, and add lemon and honey if desired.

Relieve congestion
An herbal steam inhalation with tea tree (Meleleuca alternifolia) and eucalyptus (Eucalyptus globulus) essential oils helps to loosen congestion and also fights the virus in the respiratory tract. To make a steam inhalation, pour 1 1/2 quarts of boiling water into a heatproof bowl and add 2 drops each of tea tree and eucalyptus essential oils. Lean over the bowl, using a bath towel draped over the head to capture the steam, and inhale the steam for 10 minutes.

Ease muscle aches

A hot bath with 2 cups of Epsom salts, 5 drops of eucalyptus (Eucalyptus globulus), and 5 drops of lavender (Lavandula angustifolia) essential oils will ease the muscle aches of a cold or flu. Epsom salts are rich in magnesium, a natural muscle relaxant. As a side benefit, the hot herbal steam will temporarily relieve sinus congestion.

Soothe sore throat pain
A warm gargle made from sage tea and salt eases sore throat pain and promotes healing. Sage (Salvia officinalis) contains astringent compounds, which temporarily relieve pain, and salt is mildly antiseptic. Pour 1 cup of boiling water over 2 teaspoons of dried sage, cover and steep for 10 minutes. Strain, add 1/2 teaspoon sea salt and gargle with the warm tea several times a day.

Lower a fever
To help lower a fever, soak in a tepid bath with 10 drops of lavender (Lavandula angustifolia) essential oil, or use three drops of lavender in a basin of tepid water as a sponge bath. Lavender has natural anti-inflammatory and cooling properties. A cup of hot yarrow (Achillea millefolium) and peppermint tea also will help to lower a fever by promoting perspiration. Pour 1 cup of boiling water over 1 teaspoon each of dried yarrow and peppermint; steep 10 minutes in a covered pot, strain and sip 1/4 cup every 15 minutes until the fever breaks.

Calm a cough
An herbal cough syrup of thyme and peppermint can help calm a cough. Pour 1 cup of boiling water over 1 tablespoon each of dried thyme (Thymus vulgaris) and peppermint (Mentha piperita). Cover, and steep for 20 minutes. Strain, and add 1/2 cup of honey, warming the tea gently if necessary to completely dissolve the honey. Take 1 teaspoon as often as needed.