When trying New skin / pet  products, its always best to try a small patch - wait 24 hours - , in case of allergic reaction.  

Both Cat and Dog pet shampoo bars are currently curing, it takes 4 - 6 weeks to cure soap, and these bars are a little bit softer then regular soap because they are have more conditioning to help prevent  itchy or flaky skin.

Because they are softer, it takes a bit longer to cure, closer to the six weeks, depending on humidity - longer.

Neem Oil some say it smells like old socks or garlicky, because it does, pests (fleas, ticks, mites, scabies etc..) don't like the smell of it.

How often to Bath

Also keep in mind that cats and dogs don't need to shower or bath as often as their people.

https://dogcare.dailypuppy.com/frequency-bathing-dogs-recommended-vets-3557.htm

(by clicking the above link it will open a new window)

Quoted from the above site:

"Veterinarians warn that frequent bathing strips away natural oils from a pup's skin, resulting in itching and flakes. Unless your pooch suffers from a dermatological issue or skin allergy, he needs a bath only every two to three months. Bathe a dog more frequently only if necessary, such as if he has romped outdoors and come back filthy or smelly."

Please do your own research and / or talk to your vet.