How to Help a Motion Sick Child
As the mother of a little girl who suffers terribly with motion sickness on any car ride that lasts longer than about twenty minutes, I have become intimately familiar with the battle cry of "mommy I feel sick!" I've spent countless hours combing the internet, books, and medical journal articles looking for help and have quizzed every adult I know who has suffered from motion sickness about how to help her. Here's what I've learned...I hope that it helps you and your little one.
Motion sickness is the result of the brain receiving conflicting messages from the inner ears (which control balance and equilibrium) and sensory receptors in the body and what the eyes see. The greater the conflict in signals; the greater the chance of distress. For example when a child reads a book, watches a video, or plays a handheld game in the backseat of a car, they feel the motion of the car in their inner ear and body but since her view is focused on the printed page or screen the eyes are sending the message that they are stationary. This conflicting sensory input causes confusion in the brain that triggers nausea, vomiting and other symptoms of motion sickness.
Most doctors say that motion sickness peaks between the ages of 2-12, however it can develop in infancy and some people never outgrow it.  If your baby is unusually fussy on long car rides it could be caused by motion sickness. Our daughter had her first episode of vomiting from motion sickness at 10 months old, which is when we realized that her fussiness on car trips was a symptom of feeling car sick.
Each child is different and finding the right combination of therapies is usually a matter of trying different things until you hit on the combination that best helps your child. Remember that motion sickness remedies are most effective if you begin using them before nausea starts rather than waiting until your child is already feeling ill.  The following suggestions should help you to find the right combination for your child.
Open the windows. Fresh air seems to help reduce nausea as does keeping the temperature cool. Overheating and stale air seem to worsen symptoms, so crack the windows open as much as the weather allows.
Avoid strong smells. Strong smells can trigger or exacerbate nausea and vomiting.  So try to avoid smoke, heavy perfume, exhaust fumes, factory smells etc. If possible use the "recycle" setting on the ventilation system to keep road smells outside. Aromatherapy can sometimes help, you may want try a few drops of natural citrus, lavender or peppermint essential oil on a cloth that can be sniffed as needed.
Stop frequently. Since many kids don't get sick during the first 30minutes or so of a car trip, frequent stops can reduce the likelihood of becoming ill. Be sure to let your child get out of the car for some fresh air and physical activity at each stop. This will help them to get their equilibrium back before getting back in the car.
Sit you child as far forward in the car as their age allows. For children younger than 12 sitting in the first row of rear seats rather than in the back row in a van is usually best. Encourage them to look at cars and scenery out ahead of you or have them look at the horizon. This helps to reduce the conflicting signals between the eyes and inner ear and the rear seats tend to experience the most motion. Try playing some games such as "I spy" or "license plate letter hunt" to keep them to looking out the window and keep their mind occupied. For children over 12 who are big enough to sit in the front seat safely this position should help to reduce motion sickness.
Put your child in an approved car seat or booster. Not only is a car seat critical for your child's safety, but it also helps to prevent nausea by letting them sit up high enough to see out the front window.
Avoid reading or playing video games. Reading, coloring, playing handheld games or even watching videos in thecar can trigger motion sickness or make it worse. Books on CD or games focused outside are a better bet for entertaining your child without increasing nausea.
Eat a light snack before hitting the road. When motion sickness symptoms start one of the things that happens is that digestion slows. Heavy or greasy meals before traveling or along the way can make nausea worse. Starting with an empty stomach may cause trouble too a light healthy meal or snack is likely to be your best bet.  Rather than relying on fast food on the road bring healthy snacks such as crackers, fresh veggies, fruit, or cheese sticks.
Bring a cold pack. Placing a cold pack or even a cool washcloth on the back of your child's neck the moment nausea begins to set in can be very soothing.
Try Ginger.  Have your child eat a few pieces of crystalized ginger or strong ginger candies before you start the trip and then periodically during the trip. For those old enough to swallow pills ginger capsules can work wonders as well.
Try accupressure bands. BioBands, are adjustable Velcro wrist bands with a small round bead that presses into the P6 acupressure point on the inside of the wrist. BioBands have been shown to be so effective in treating motion sickness (and other types of nausea) that they have received FDA marketing clearance. 
Keep plenty of lollipops on hand. Sucking on a lollipop in flavors known to reduce nausea can work wonders and it is one treatment that your child will love! CarSickKids.com carries Queasy Pop Kids which are specially formulated to help relieve motion sickness and also Yummy Earth Organic lollipops in flavors known to ease nausea for those children whose parents prefer organic product and those who cannot eat products containing corn syrup. (As nearly every other lollipop on the market does.)
Be prepared for the worst. No matter what treatments you try it is still important to be prepared for unexpected vomiting. Knowing that they have a safe place to get sick if they need to will help to keep your child calm and will in turn keep everyone else in the car more comfortable as well. Keep a supply of sturdy , leak proof, bags in the car for emergencies, plus wet wipes for cleanups and a fresh change of clothes in case it is needed. The Red E Bag is a perfect solution for unexpected (or not so unexpected) vomiting.  It is a reusable sickness bag with disposable, leak proof, liners and space to store the rest of your motion sickness supplies.
CarSickKids.com offers a full range of products to prevent and treat motion sickness. Check out the Motion Siskness Starter Set: a complete self-contained kit that will keep you organized and prepared to help any family member who is prone to motion sickness.