I'm not sure about natural preventatives. I have tried various lotions and potions and none have worked to date.
We use Frontline Spot On for fleas and ticks. I have two pets (1 dog and 1 cat) with flea allergies so not treating is a non-option. I don't like using chemical products on them but it works so I cannot complain. If I didn't treat I'd have one bald cat and one dog that won't stop licking and scratching.
My dogs get wet (often soaked) on a near daily basis through the spring/summer/autumn and the Frontline has proved to be very effective. The important thing to do is NOT allow them to swim for at least 48 hours after the application.
Well I live in the netherlands and probably its a lot colder over here so there are less ticks and flees. I never used a chemical substance on Gollum, i raw feed her and give her garlic with the veggies mix and i never saw a flee on her. I picked 3 ticks from her coat in the whole year we have her, and comb her regularly.
I have always used Advantix- Sammi swims all the time and we have never had a flea promblem or seen a tick on her. We do alot of hiking in the fields so I'm sold! You can't use Advantix if you have cats though. Oh yeah wanted to add, you just shouldnt let them in the water for a couple of days after applying!
We just started Sentinel (fleas & worms), which is a monthly pill. Disadvantage; doesn't kill adult fleas, only makes any eggs they lay not able to develop, so you can't get an infestation. We spread Diatomaceous Earth (food grade) on the grass outside to hopefully kill any adults. We saw 3 fleas on Jonah the night we brought him home from the breeder's house (1 month ago) and haven't seen one since. Our backup if he does get a lot of adult fleas would be a dose of Capstar, and then re-evaluate at that time. Our previous lab was on Program, which was a similar flea prevention (didn't kill adults, only made them sterile), and we never had fleas in 5 years with her. We live in south Florida, so we have to treat year round as we don't get cool weather!
I didn't want Advantix or Frontline because I have small children I didn't want touching the dog after I put it on him (transferring the chemical from him to themselves, their mouths, toys, etc). Since the Sentinal is a pill, I don't have to worry about that!