How does one assign multiple values to the "activeIngredient" schema tag?

Question

I want to use the activeIngredient property http://health-lifesci.schema.org/activeIngredient to list two active ingredients. What is the proper way to mark it up?

And once it is properly marked up, should it appear in the Google Structured author tool as 2 values assigned to 1 property, as shown below:

activeIngredient     ingredient 1, ingredient 2 

or, does the activeIngredient property need to appear twice, as shown below:

activeIngredient     ingredient 1

activeIngredient     ingredient 2

The link below shows an example where the activeIngredient property is used to describe a single ingredient. It appears at the bottom third of the page. https://search.google.com/structured-data/testing-tool/u/0/#url=http%3A%2F%2Fwww.aleve.com%2F

Answer 1

Unless its description says otherwise (example: keywords), a Schema.org property always takes a single value.

If you want to provide multiple values, you have to repeat the property (in case of Microdata and RDFa) or provide an array value (in case of JSON-LD).

So activeIngredient is for one active ingredient. Multiple active ingredients could be specified like this:

<ul>
  <li itemprop="activeIngredient">ingredient 1</li>
  <li itemprop="activeIngredient">ingredient 2</li>
</ul>

<ul>
  <li property="activeIngredient">ingredient 1</li>
  <li property="activeIngredient">ingredient 2</li>
</ul>

"activeIngredient": 
[
  "ingredient 1",
  "ingredient 2"
]