Permethrin is an insecticide and a repellent. It is usually used to treat clothing. It is not applied to the skin.

DEET is a very effective repellent. It can be applied to the skin.

In bad tick areas, spray clothing with Permethrin at home before you go. Permethrin will last a couple of weeks (or longer).
Apply DEET on site, especially to those areas around the waist and lower legs for ticks. DEET will need to be reapplied after a few hours.

Picaridin is a newer repellent. It is the next best thing to DEET. It doesn't smell as bad, causes less skin irritation and does not melt some plastics like DEET does. Picaridin is probably the best alternative to DEET for those with sensitive skin or for small children. There are differences of opinion on Picaridin. It may be as effective as DEET for mosquitoes, probably not as good for ticks?