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 mask, it is not rinsed off : the hair serum typically remains in place in most cases to provide prolonged action. Formulations are generally lightweight, often aqueous when intended for the scalp, and potentially richer and more oily when aimed at the hair fibre. This diversity of textures reflects the range of uses of hair serums : soothing an irritated scalp, rebalancing excessive sebum production, strengthening the roots, smoothing the cuticles, protecting split ends or imparting shine.

We distinguish two main categories of hair serums : those applied to the scalp and those formulated for the lengths and ends. Each category comprises several subtypes, based on the specific concerns targeted.

Scalp serums.

Regarding the scalp, several serums are available. The anti‐dandruff serums often combine mild keratolytic agents, such as salicylic acid, with antifungal agents, such as the ciclopirox olamine or the 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 hair-loss prevention serums. Despite these various names, they are essentially the same products. They generally contain active ingredients that stimulate blood circulation, such as caffeine, in order to optimise the delivery of nutrients and oxygen to the hair bulbs, and ingredients that reinforce the anchorage of the hair follicles, such as certain peptides. That said, although these serums can contribute, to a certain extent, to stimulating the hair growth, their effects remain more limited than those of medico-aesthetic approaches such as PRP (platelet-rich plasma). Moreover, no method can increase 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, whilst avoiding over-stripping the skin so as not to induce a rebound effect. In practice, these formulations often combine sebum-regulating agents, such as zinc or niacinamide, with soothing actives that reduce inflammation linked to hyperseborrhoea. The aim is to restore a healthy scalp that doesn’t become greasy too quickly.

Serums for hair lengths.

As for serums intended for the lengths, they primarily aim to enhance the appearance and strength of the hair fibre. Notably, there are hydrating serums, which provide suppleness by limiting water loss, and fortifying serums that strengthen the cuticle to reduce breakage. In practice, these two actions are closely linked, which explains why many products claim both hydrating and protective properties.

The majority of these hair serums also target frizz : they contain film-forming agents, such as polymers that smooth the cuticle surface and prevent moisture from penetrating the fibre, which is responsible for irregular hair swelling. Some are even marketed as smoothing serums, which is slightly misleading. In reality, these treatments do not alter the hair’s natural shape but help to control its texture. Only a heated styling tool can achieve a sleek finish at home. Some are also supplied with heat-protective serums designed to shield the hair fibres from high temperatures.

The method of using a hair serum depends on both the type of serum and the intended outcome. For scalp serums, it is generally recommended to apply them to clean hair, preferably after shampooing. Only a small amount is needed. Dispense a few drops onto your scalp, spreading them evenly, then gently massage with your fingertips to facilitate absorption. Depending on the serum, application may be daily or a few times a week, in accordance with the manufacturer’s instructions. Most hair serums are leave-in, though this is not always the case.

For hair serums intended for the mid-lengths, application is most often on towel-dried or dry hair, in small quantities on the ends, avoiding the roots so as not to weigh down the scalp. To do this, place a few drops in the hollow of your palms, rub them together, then distribute the product strand by strand.

Patience and consistency are the keys to obtaining results when using hair serums.

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

However, as with any cosmetic product, certain precautions must 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 can be irritating to these individuals and cause redness and itching, especially if the skin barrier is weakened.

In order to prevent any risk of a systemic reaction, we recommend that you test your hair serum on a small area of skin upon initial use: apply a few drops to the crease of your elbow, for example, and wait 24 to 48 hours. Should you experience an allergic reaction, do not use it on your scalp. Additionally, during the pregnancy and breastfeeding, the precautions are the same as for skincare: it is not recommended to use hair serums containing retinoids or essential oils.

Avoid using multiple scalp serums at the same time so that their respective effects do not neutralise one another. It is better to apply one in the morning and the other in the evening.

Regarding hair serums for the lengths and ends, the risks are lower since they are applied to the hair fibre, a non-living keratinised tissue. However, their safety also depends on proper use: avoid, for example, applying a serum intended for the lengths directly onto the scalp, and be careful that the product does not migrate onto the face, particularly if you wear your hair loose in windy conditions. Overall, the risk of genuine 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% naturally sourced ingredients, this non-greasy formula hydrates and strengthens the hair fibre to reduce breakage and impart shine and softness to the hair. What’s the extra benefit of this serum? It contains mother-of-pearl particles that reflect light to provide a satiny sheen to the hair and intensify its radiance.