Probiotics are particularly important for supporting our immune system. The human gut has approximately 500 different species of these beneficial bacteria which outnumber our cells 10:1 and we are only now beginning to understand everything that they do for us. Choose a formulation that contains human-strains and is dairy-free when possible. Probiotics are safe for all ages including infants.
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.
For information about the benefits probiotics on allergies, check out this post.