Before traveling you should assemble a mini-emergency kit, especially if you are in a very rural or distant location.
Here are some things you should include in your kit:
Pedialyte Powder packs – just add water and you have a replenishing clear liquid in the event of vomiting or diarrhea
Topicals – 1% hydrocortisone for itchy rashes or bug bites and topical Neosporin or Bacitracin for scrapes and cuts
Diphenhydramine (Benadryl) for hives, allergy symptoms
Epi-Pen (Jr) – bring 6 if you are traveling and your child has food allergies/history of anaphylaxis
If your child has asthma, bring an inhaler/spacer with you, especially if on a plane. Check with the airline whether there are plugs available in the event your child requires a nebulizer treatment on board (and make sure you bring on tubing, mask, meds along with your nebulizer)
If you are traveling with a baby, take saline drops and a device like the SnotSucker to empty the nose of mucous, especially to facilitate drinking/hydration
If your child is prone to ear infections, and you are flying, your doctor may want you to bring a prescription antibiotic with you, as well as ear drops for pain, and others for swimmers ear
Ask your doctor about medications for motion sickness or nausea/vomiting and pack those with you.
Make sure your child’s vaccines are up to date, especially with international travel