This year I have discovered a garlic-based syrup that has done wonders for my kids (they haven't had a single thing since started back to preschool in Sept., and they were aways on antibiotics for bronchitis and the like over the winter before). It's dead easy to make and safe to take. Here goes:
1 bulb of garlic, crush/chop all cloves
Add juice of 1 whole lemon, 4 spoonfuls of honey (vary this according to how sweet you need/like it) and about 250ml cooled boiled water. Mix it all up, leave to stand in fridge for 24 hrs and then sieve into a jar/bottle.
I gave my kids 1 dessert spoonful morning and evening every day till they were prety much invincible and now they get it once a day and not at weekends (apparently garlic is pretty hard on the liver). When you are feeling rough you can take 1 spoonful every 4 hrs or so.
My aunt took it when she was recovering from flu and she said it worked wonders too. (i'm never ill so don't need it).
Good luck, hope it works for you.