Nausea medications often cause drowsiness, blurred vision, dry mouth, and may cause spasms in the neck, jaw, or tongue.
DiphenhydramineSince diphenhydramine is the best of the allergy medications, it will probably already be in your first aid kit. The problem with using diphenhydramine as a nausea medication is the same as using it for allergies; it causes drowsiness. Not for use in kids under 6 years old.
CyclizineThe oldest of the antihistamines approved as nausea medications. Cyclizine causes drowsiness much like diphenhydramine does. Cyclizine is also not for use in kids under 6.
DimenhydrinateDimenhydrinate is the most common OTC nausea medication. It's used primarily to combat motion sickness. Dimenhydrinate still causes drowsiness like the others above, but it is OK to use in kids as young as 2 years old.
MeclizineThe newest nausea medication to be approved for sale over the counter, meclizine has long been used as a prescription for vertigo. It is also useful for non-medical causes of motion sickness, like rocking boats or turbulent airplanes. Meclizine's more recent past as a prescription-only nausea medication means it may be more expensive than dimenhydrinate. Meclizine is not for use in kids under 12.
For more information on nausea treatment, see How to Treat Nausea