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.
But for kids that love them, Johnny Jump Ups can be a great place to play. They are generally recommended for children around the age of 6 months (Though the official recommendation from Evenflo is 4 months.) until walking and weighing no more than 24 pounds.