The claim that makes it a drug
On this page8
Why it is the common failure
It is what the customer wants to hear. A beard oil that conditions is a nice product; a beard oil that grows a beard is a solution to a problem, and the temptation to describe it that way does not come from carelessness.
What it does legally
It makes the product one intended to affect a function of the body, which is the drug definition. A drug marketed without the applicable approval or monograph compliance is not a cosmetic with a strong claim; it is an unapproved drug.
The near misses matter too
"Stimulates follicles", "promotes growth", "fuller coverage over time", "fills in patches". Each is a statement about what the body will do, and swapping the verb does not change the claim being made.
What you can say instead
What the product does to the hair that is already there, and how it looks and feels. Conditions, softens, tames, adds shine, controls, scents, holds. Those are appearance and attractiveness claims and they sit inside the cosmetic definition.
The claim is not only on the label
Intended use is established from claims generally, and from consumer expectations. A product page, a social post, an answer in a review and a market stall sign all speak to intended use. The regulated sentence is not confined to the artwork.
Ingredients can make the claim for you
FDA names certain ingredients as a factor in establishing intended use. An ingredient with a known therapeutic use can establish a drug intent even where the copy is careful, which is worth knowing before you build a brand on one.
Where this ends up
For almost every small maker, the correct answer is to stay a cosmetic deliberately and to write copy that is specific about feel, scent and appearance. The specificity is what sells it anyway.