I think tick shampoos for cats and dogs are generally safe when you follow the directions. I agree with the article that you need to be extra careful when using tick shampoo on animals under 6 months old. Puppies and kittens can be very sensitive.
When you read the ingredients of the average pet shampoo the names of the additives are not as scary as some of the ones you find on the labels of some powders and flee collars. Still, if you are concerned then you should definitely look for a product with natural ingredients.
One of the best shampoos I have found contains citronella oil, the same thing we use to repel mosquitoes. The citronella oil's effectiveness in warding off ticks is believed to be mainly due to its smell. The odor makes it difficult for ticks to find your pet. And the great thing about citronella is that it is safe for your pet, your family and the environment.