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.
106. I put my daughter in one from 5 months but 4 months may be a little early. I'd wait until he is able to sit up well without support. When you do decide to put him in it just make sure you keep it short (eg 15 minutes max a day) and that his feet are flat on the floor (to prevent him from walking on his tip toes).i. My son was in the jumperoo at 4 months and in a walker a month later (mainly because I hadn't heard of them before otherwise I would have put him in the walker sooner as I would have felt better as it doesn't bounce).