This is what I have been working with lately-anti-viral and antibiotic herbs. My main reason is because of my Dad-I want to boost his immunity after his chemo treatments are over so his body will be strong enough to keep fighting. But this is also timely since the flu season has been so bad and the CDC guessed wrong on the flu vaccine for this year.
I have been getting very disturbing emails from customers interested in protecting their kids with essential oils, most wanting to run advice by me that they had received from MLM reps. But essential oils are metabolized very quickly by the body and really need to come into direct with the germs to kill them. The best way ALWAYS to fight infection is to keep your natural immunity strong so your body can defend against invaders on its own.
Echinacea is a popular herb but it's just never used properly, and the species commonly available is the least effective. I like boneset. Used at the first signs of infection it can short circuit the infection and stop it from taking hold. The dried herb is easily available and you can probably find it growing wild in fields and near streams. I really recommend making it into an alcohol based extract because it's really bitter!
Eupatorium perfoliatum comes from. It can be found in the eastern 2/3 of the United States. This is a very important herb and I really recommend getting some and preparing your remedies ahead of time so they're ready when you need them.
Even better is to keep the immune system strong in the first place. For that I recommend astragalus root. It's considered an adaptogen and is sometimes called "young man's ginseng". it has no known toxicity in any dose that I have ever seen and builds up the immune system by building strong bone marrow and it also tones the lungs and kidneys. It's best used as a preventative and should probably not be used during an active infection. You can buy it by the pound (organic and kosher certified) from Mountain Rose Herbs for $16/lb , which should last quite a while. I like to buy the sliced roots-they look like tongue depressors at the doctor's office. This is a really versatile herb, and pleasant tasting and can be used in teas, extracts or you can toss a few slices into stews and broth and let them simmer and remove them before serving.
I also recommend HERBAL HEALING FOR CHILDREN and 475 HERBAL AND AROMATHERAPY RECIPES by Demetria Clark. Rosemary Gladstar has lots of books that are a joy to read and all of these books are available in book form and for kindle on amazon.com.