Ginger is a diaphoretic which means it will encourage sweating with the onset of a cold to assist the body in fighting the pathogen. It is also a good choice when feeling nauseated and its anti-inflammatory properties are soothing to sore throats.
This is a great immune boosting tea blend recipe containing ginger and other ingredients.
Tips for maintaing health while travelling are available here. Read this post to find out the difference between cold, flu's and allergies. For information about preventing allergies, check out this post. Tips for preventing colds and flu's can be found here and about preventing the spread of colds and flu's here.