Everything you need to know about hair serums.

Hair serum is a concentrated treatment formulated to address specific needs, whether along the hair lengths or on the scalp.

Unlike a conditioner or a mask, it does not rinse out : hair serum remains, in the vast majority of cases, applied to deliver a sustained effect. The formulations are typically lightweight, often aqueous when formulated for the scalp, and occasionally richer and more oily when targeting the hair fiber. This diversity of textures mirrors the wide range of applications for hair serums : to soothe an irritated scalp, to rebalance excessive sebum production, to strengthen the roots, to smooth cuticle layers, to protect split ends, or to enhance shine.

We distinguish two major families of hair serums : those applied to the scalp and those designed for lengths and ends. Each category encompasses several subtypes, depending on the targeted concerns.

Scalp serums.

With regard to the scalp, several serums are available. The anti-dandruff serums often combine mild keratolytic active ingredients, such as salicylic acid, with antifungal agents, such as ciclopirox olamine or piroctone olamine. They are generally used alongside anti-dandruff shampoos and for maintenance, to prevent relapse.

There are also hair growth serums, sometimes referred to as hair regrowth serums or anti-hair-loss serums. Despite these different labels, they are equivalent products. They typically contain actives that enhance blood circulation, such as caffeine, to optimize nutrient and oxygen delivery to the hair bulbs, and ingredients that reinforce follicular anchoring, such as specific peptides. That said, while these serums may help to some extent to stimulate the hair growth, their effects remain more limited compared to medico-aesthetic treatments like PRP (platelet-rich plasma). Moreover, no method can accelerate the rate of hair growth beyond the limits set by genetics.

Finally, the rebalancing serums for oily scalps rely on purifying and mattifying ingredients to limit excessive sebum production by the sebaceous glands, while avoiding stripping the skin to prevent rebound effects. In practice, these formulas often combine sebum-regulating agents, such as zinc or niacinamide, along with soothing actives that reduce inflammations related to hyperseborrhea. The goal is to restore a healthy scalp that does not become oily too quickly.

Serums for hair lengths.

As for serums formulated for the hair lengths, they are primarily designed to improve the appearance and strength of the hair fiber. Notably, there are hydrating serums, which add flexibility by reducing water loss, and fortifying serums that reinforce the cuticle to minimize breakage. In practice, these two functions are closely linked, which is why many products claim both moisturizing and protective benefits.

Most of these hair serums also target frizz : they contain film-forming agents, such as polymers, which smooth the cuticle surface and prevent moisture from penetrating the fiber responsible for uneven hair swelling. Some are even marketed as smoothing serums, which is somewhat misleading. In reality, these treatments do not alter the hair's natural shape but help to control the fiber. Only a heated tool can produce a straightening effect at home. Some are also offered with heat-protective serums designed to protect the hair fibers from high temperatures.

The method of using a hair serum depends on both the type of serum and the desired outcome. For serums formulated for the scalp, it is generally recommended to apply them to clean hair, ideally after shampooing. A small amount is sufficient. Dispense a few drops onto your scalp, attempt to distribute them evenly, then gently massage with your fingertips to enhance product absorption. Depending on the serum formulation, application can be daily or several times per week, following the manufacturer’s guidelines. Most hair serums are designed as leave-in treatments, but this is not always the case.

For hair serums used on the lengths, application is most often done on towel-dried or dry hair, in small amounts on the ends, avoiding the roots to prevent weighing down the scalp. To do this, place a few drops in the palm of your hands, rub them together, then distribute the product strand by strand.

Patience and consistency are the key to achieving results when using hair serums.

In absolute terms, hair serums are well tolerated and do not present any major contraindications.

However, as with any cosmetic product, certain precautions should be taken. Indeed, depending on their composition, scalp serums may not be suitable for individuals with a sensitive scalp or prone to eczema. Products highly concentrated in essential oils or alcohols may be irritating to these individuals and cause redness and itching, especially if the skin barrier is compromised.

To prevent any risk of a systemic reaction, we recommend that you patch test your hair serum on a small area of skin before first use: apply a few drops to the inside of your elbow, for example, and wait 24 to 48 hours. If you notice an allergic reaction, do not use it on your scalp. Furthermore, during the pregnancy and breastfeeding, the same precautions apply as for skincare: hair serums containing retinoids or essential oils are not recommended.

Avoid simultaneously applying multiple scalp serums to prevent their respective effects from neutralizing each other. It is preferable to use one in the morning and the other in the evening.

Regarding hair serums for lengths and ends, the risks are lower since they are applied to the hair fiber, a non-living keratinized tissue. However, their safety also depends on proper use: for example, avoid applying a serum formulated for lengths directly onto the scalp, and be sure the product does not migrate to the face, especially if you wear your hair down on windy days. Overall, the risk of true skin irritation remains low, but it is best to follow the manufacturers' recommendations.

At Typology, we offer a restorative hair serum enriched with hyaluronic acid and plant-based keratin. Composed of 99% natural-origin ingredients, this non-greasy formula hydrates and strengthens the hair fiber to reduce breakage while imparting shine and softness. What’s the serum’s added benefit? It contains pearlescent pigments that reflect light to deliver a satin glow to the hair and intensify its shine.