When dealing with a headache, try boiling one cup of apple cider vinegar and one cup of water in a pot. Pour into a heat proof bowl and put on the table or other safe place that you can lean over the bowl and cover your head with a towel. Inhale the steam for a few minutes to bring some relief.
The warning on mine says not to use prior to 4 months of age. My son was in his Jolly Jumper from 3 months. The directions of use are that if they can confidently hold up their head then they are fine.
Children should remain in a booster seat until adult seat belts fit properly (usually when the child reaches about 4 feet 9 inches in height and is between 8 and 12 years of age). Since children vary in size, safety experts urge parents to use the weight and height restrictions instead of the age guidelines.