Since both serums and ampoules are concentrated formulas to address specific skin care problems, it's easy to mix them up. In addition, these are not regulated terms of beauty. Usually the brand has to decide whether to market their product as a serum or an ampoule.
But in general, you can think of ampoules as potent, charged serums. In most cases, they have a higher concentration of active ingredients without fillers or preservatives. Therefore, they are supplied in single doses in tiny vials that should be used sparingly for special occasions.
"I compare it to exercise," says Alicia Yoon, prominent beautician and founder of Peach & Lily. "Think of serums as your daily exercise routine. Ampoules are the intense fitness class you really lean into to target a stubborn area."
But here, too, there are no strict guidelines for an ampoule compared to a serum. "Whatever the active ingredient is, if it's on the high end of the spectrum, I think I'd treat this more like an ampoule, even if the brand calls it a serum," adds Yoon. On the other hand, you will find products that are marketed as "daily ampoules" that are actually formulated a little closer to serums.