Susan Blum, MD, functional medicine specialist and author of The Immune System Recovery Plan

"At the first sign of a cold, I take Vitamin A drops. Not beta carotene, but the pre-formed kind of Vitamin A called retinyl palmitate. It stimulates the activity of the immune cells that fight viruses. I take a very high dose—100,000 IU—per day for 3 days and it works like a charm, better than anything else! The only caveat: This type of high dose shouldn’t be used for extended periods of time unless you’re under a doctor’s supervision. You shouldn't take it if you are or think you are pregnant."

Alexander Kulick, MD, integrative medicine practitioner

"I use and recommend Host Defense MyCommunity Extract from Fungi Perfecti. It’s a blend of 17 mushrooms like reishi, cordyceps, and shitake, and if you take 2 dropper-fulls in water 2 to 3 times on the first day you feel sick, it can abort the attack. Mushrooms contain polysaccharides called beta-glucans that research shows boost the immune system. I also advise using it before a flight, when germ exposure is high due to the re-circulated air in the cabin."

Clara Charny, DC, naturopath and founder of Charny Healing Center

"Supplements that support the immune system help, but so will a 20-minute detox foot bath with mustard powder and essential oils like eucalyptus and rosemary. It’s an old folk remedy that’s been used in Eastern Europe, China, and India. We eliminate toxins through our feet and this combination heats up the body and increases circulation, helping to draw out the virus. For a little soreness in the throat, gargling with something alkalizing like honey and apple cider vinegar (one tablespoon of each dissolved in warm water) will help, too. Do both right when you feel sick, then put socks on and go to bed."

Haylie Pomroy, nutritionist and author of The Fast Metabolism Diet

"An old Ayurvedic remedy is to dab almond oil in the nostrils before you’re around groups of people who may be sick—like on a plane or at the gym. It acts as a barrier and helps prevent you from contracting the virus through inhalation. If I’m starting to feel sick, my secret is called Lomatium root. It’s my go-to because it’s anti-viral and studies have shown it increases the body’s natural killer cells. I like the liquid tincture from Wise Women Herbals. Take 25 drops twice a day when you first feel symptoms."

Jeffrey Morrison, MD, CNS, founder of The Morrison Center in Manhattan

"Vitamin C is my favorite remedy when I’m fighting a cold. I recommend 1000mg an hour for at least 1 to 2 days. When you’re healthy, 6 grams is usually the most you can absorb in a day, but when your body is fighting an infection that amount can double. That means we can absorb 10-12 grams a day. A sign of not absorbing Vitamin C is a loose stool, that’s how you know you’ve reached your max."

Emily Feurring, certified holistic health coach and brand evangelist for Creative Juice

"Ginger is an amazing, natural way to fight off a cold. It has antioxidant and anti-inflammatory benefits, which help fight infection and enhance immune function. We blend it into many of our cold-pressed juices. My favorite flu fighter is our No. 3 Carrot-Green Apple with ginger, but I’ll brew fresh ginger root into a tea at home as well. You just steep 4-6 slices of ginger in boiling water for 10-15 minutes. If your throat needs soothing you can add honey and lemon to taste."

Urvi Radia, homeopath, The Organic Pharmacy in Beverly Hills

"Elderberry, an herb from the honeysuckle family, is excellent for strengthening immunity. At this time of year when everyone is coming down with colds or getting the flu, we get multiple orders a day for our Immune Tonic with elderberry. Take 15 drops in water twice a day to help increase the body’s defense cells. Elderberry is also safe to take on a regular basis, unlike some other immune-boosting herbs."