It occurs both ways on the Internet and also with and without the hyphen. I would say "soothing effect" for skin.
Student or Learner
"Ylang-Ylang" is a component for cosmetics. Which is better between "Ylang-ylang" and "Ylang-Ylang"? Can the second word in a composite noun be capitalized for impression?
Ylang-Ylang Hand Cream with propolis is excellent for moisturizing and has a calming effect for skin
With a given name, your are free to call it as you like, for impact.. Names should be in capitals letters even when hyphenated.
Not a teacher
It calls for neither capitalisation nor for a hyphen.
My hand cream is made of ylang ylang, tea tree and shea butter.
However, the words written on an actual tube of hand cream would probably be capitalised because they are seen as the "title" or official name of the product.
It would probably read "Ylang Ylang Hand Cream" on the tube and on the shelf in a shop. If you wrote it in a normal sentence, however, it would be "I have just bought a tube of ylang ylang hand cream. It smells divine".
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.