Here is the official definition from the The International Cosmetic Ingredient Dictionary and Handbook:

“Aroma is a term for ingredient labeling used to identify that a product contains a material or combination of materials normally added to a cosmetic to produce or to mask a particular flavor.”

INCI shows the only purpose of aroma to be "flavouring".

However, due to regulation differences, some companies may use aroma in place of parfum.

In Canada, this ingredient only has to be listed in concentrations above 1%.

Ethylhexyl Palmitate is also used to help improve the texture of cosmetics. It helps other ingredient dissolve in products and help disperse ingredients more evenly.

You'll likely find this ingredient in sunscreen, as it is often used to mix UV-blocking ingredients such as avobenzone and ethylhexyl triazone.

It can also help stabilize the fragrances in a product as a fragrance fixative.

Ethylhexyl Palmitate can be used to substitute mineral oil.

Due to its high fatty acid content, it may not be fungal-acne safe.

Because it’s oil-soluble, THD dives deep into your skin’s fatty layers (think ceramides and cholesterol) to fight off the kind of free radicals that mess with your skin barrier. This makes it a great pair with water-based vitamin C (ascorbic acid) that mainly works on the surface.

Even at just 0.1%, THD is already showing great antioxidant activity. When used up to 2%, it helps keep your skin happy and calm, especially when it’s stressed from pollution or sun.

Want to fade dark spots or tackle hyperpigmentation? You’ll want 5% or more. Pairing it with brightening buddies like niacinamide or licorice root gives even better results. One study even used 30% THD with other brighteners and saw real results on stubborn discoloration, even in melasma-prone skin.

A note on THD: It’s has a slightly silky, oily texture and usually shows up colorless or pale yellow (though the exact shade can vary by supplier).

While you can sneak it into water-based formulas, it really shines when paired with silicones or oils, which help your skin soak it up better.

THD is pretty stable, but it’s still vulnerable to degradation like ascorbic acid. Too much light or heat (above 113°F / 45°C) can break it down over time. Go for dark and opaque packaging that keeps it safe and shady!

Read more about other types of Vitamin C: