Common cold may sometimes be due to weak digestion. When the food we eat is not fully digested, it transforms into mucus known as ama (toxin). This circulates through the body and reaches the respiratory system, where it causes colds. 

Diet:

Cold food and drinks, ice creams, sweets, fried food and milk products (cheese, creams, yoghurt) should not be consumed. Sweet fruit juices should also be avoided. Bread, meats, nuts and pastries are also not good to take. 
Follow a light and warm diets like boiled or steamed vegetables and vegetable soup. Spice teas, herbal teas and hot milk can be taken (if boiled with a piece of crushed ginger). Half a teaspoon of turmeric powder can be mixed with the milk. 

Home Remedies

• Take ½ teaspoon of ginger powder with 1 teaspoon of honey. Black pepper can also be added.
• Chewing a piece of fresh ginger with a little salt on it will ease coughs.
• Half a cup of warm water mixed with one teaspoon of lemon juice and one teaspoon of honey can be taken several times a day.
• Equal quantities of powdered fenugreek seeds, turmeric and ginger powder can be mixed together. One teaspoon can be taken in the morning and evening.
• In cases of a sore throat, a clove or two cardamoms or a few raisins can be chewed.
• Gargling with warm salty water is also beneficial. This can be done two or three times a day.