"We are planing to travel to Brasil in March, as you know it has been a lot of new disease with Zika and dengue mosquitos. We are be worried about the travel as we have two children 4 and 10, so could we use the Repel 100 onto children skins? is it safe?"
Zika and dengue fever are carried by the same variety of mosquito so a repellent for one is also effective against the other. You can treat the 10 year old as an adult so far as repellents are concerned. The recommendation for minimum age for DEET products vary by country but is generally 2-3 years for lower concentration products. Personally I would try and avoid using high concentration DEET products altogether, whether on adult or child.
High concentration DEET does not actually protect more than a 50% concentration though it may last longer between applications. In some parts of the world insects have developed a tolerance to DEET.
We think you can get all the protection you need from non DEET repellents such as those based on 20% Saltidin or Citriodiol which don't have all the negative side effects of DEET and aren't absorbed by the body.
We recommend you take at least two types of repellent from: Saltidin, Citriodiol or DEET. Use the one you prefer best. Re-apply the repellent as soon as insects start taking an interest in you. If they persist, despite re-application, use you're 2nd choice repellent. It's extremely unlikely that insects will be tolerant to both. If you want to take DEET for peace of mind, that's fine, but try to have it as your stand-by repellent.
We've put a lot more information on these pages:
This page shows the different types and links to the shopping page.
How to use repellents.
Other information that will help you avoid being bitten.