Serums are lightweight products that do not have the thickness or greasiness of a cream or lotion.
Creams or lotions are heavier because they are designed to adhere to the skin to help maintain hydration.
Serums usually have other active ingredients in them designed to address a particular concern. For example, discoloration and anti-aging are the most common. These active ingredients are more concentrated and will therefore be a bit more potent.
Because these active ingredients are so concentrated they can be a bit more irritating for some skin types depending on the active ingredients.
Most who consider serums will use particular products to address specific concerns. Most often these are used on the face because the products are much costlier and can be cost inhibitive to use on larger surface areas like the body.
Serums can be be used alone for people with oily skin and feel that they prefer the lightweight feel of these products. However, by applying a serum first and traditional moisturizer on top this can help make the serum more effective and reduce any associated irritation.
Most body serums are targeting the one of the most frustrating cosmetic concerns- tissue paper like wrinkling of the skin. They often contain peptides and alpha hydroxy acids with claims to firm and tighten the skin. These are ideally used with a moisturizer as most people that complain of these concerns rarely complain about oily skin in these areas- it’s usually excessively dry!
There are also body serums that target excessively dry skin without leaving behind a greasy feel. These are the ones I like the most because one of the biggest barriers to using moisturizers in the first place is how greasy they can feel. These body serums have concentrated hydrating ingredients that are not irritating. It’s true that it will make them even more potent to use with a moisturizer but if you just don’t like greasy products, these are perfectly ok on their own.