Astragalus root has long been used in traditional Chinese medicine to strengthen immunity and prevent colds and flu. Studies have found that astragalus has antiviral properties and stimulates the immune system, although there have been no clinical trials examining the effectiveness of astragalus against colds in humans.

Garlic is one of the more popular home cures for colds. Many cultures have a home remedy for the cold using garlic, whether it’s chicken soup with lots of garlic, a drink made with raw crushed garlic, or if it just involves eating raw garlic.
The cold-fighting compound in garlic is thought to be allicin, which has demonstrated antibacterial and antifungal properties. Allicin is what gives garlic its distinctive hot flavor. To maximize the amount of allicin, fresh garlic should be chopped or crushed and it should be raw. It’s also available in pill form.

Honey is a popular home remedy for cough and colds in many cultures. A new study in the Archives of Pediatrics and Adolescent Medicine provides the first evidence showing that honey may help to calm children's coughs and help them sleep better. Researchers gave 105 children with colds eith honey, honey-flavored cough medicine or no treatment. All of the children got better, but honey consistently scored best in parents' rating of their children's cough symptoms.

Ginger root is another folk remedy for cough, colds and sore throat. It's used in traditional Chinese medicine to treat coughs and is also for colds accompanied by runny nose with a clear nasal discharge, headache, neck and shoulder aches, and a white tongue coating. In ayurveda, the traditional medicine of India, ginger is also used for cough and colds.

Onion is a close to garlic biologically and contains many similar antiviral chemicals. 
Steep raw onion slices overnight in honey. Take the resulting mixture at intervals like a cough syrup. You can also use more onions in cooking whenever you have a cold.

Anise Commission E in Germany recommended aniseed as an expectorant for getting rid of phlegm. In large doses, it also has some antiviral benefits.

Goldenseal increases the blood supply to the spleen, an organ that's the staging area for the fighting cells of your immune system. It is antiseptic and immune stimulating.
The major healing component in goldenseal, berberine, activates special white blood cells (macrophages) that are responsible for destroying bacteria, fungi, viruses and tumor cells. Several related chemicals in the herb appear to help the berberine do its job.

Licorice contains antiviral compounds that induce the release of interferons, the body's own antiviral constituents