Psoriasis of the scalp: how to reduce flare-ups?

Psoriasis is a systemic and chronic inflammatory skin eruption. It presents as red, thick plaques that shed. Psoriasis is characterised by an excessive renewal and accumulation of epidermal cells, leading to a local inflammation . This disease tends to affect adults, with a peak onset generally between 20 and 40 years of age. Histological analyses show an increase in the thickness of the epidermis (acanthosis) and incomplete differentiation of keratinocytes (parakeratosis). Its manifestation is triggered by the combination of several risk factors. These include the immune system, genetic predisposition, and environmental factors. The causes of scalp psoriasis can be summarised by these three factors. Psoriasis can appear on various areas, notably the scalp. This is the most common location accounting for 50 to 80% of psoriasis cases.

The symptoms of scalp psoriasis relate to the following elements:

• The emergence of red patches of varying thickness on the scalp. They never extend more than 2 cm from the edge of the scalp;

• Formation of whitish scales and flakes (dandruff) behind the ears, the nape, the forehead and the scalp;

• Feeling of itchiness accompanied by flaking, sometimes with bleeding;

• Cicatricial alopecia for the most severe cases.

Psoriasis is a disease that cannot be cured, but it can be managed. Some treatments proposed by professionals can space out flare-ups over several months or even years. It should be noted that scalp psoriasis can manifest in various areas. It can disappear completely, but recurrences are not uncommon.

Medicinal treatments for this chronic inflammatory disease are administered based on the severity of its onset. In the case of localised scalp psoriasis, for example, local treatments may be prescribed by the dermatologist. Here are a few examples:

• Use of lotions or shampoos containing dermocorticoids. Locally applied, dermocorticoids help to soothe the skin by combating inflammation. They inhibit the NF-kB transcription factor by activating the transcription of the IkB gene, thus providing anti-inflammatory effects;

• Use of Tazarotene which is a retinoid derived from Vitamin A: it regulates the differentiation of keratinocytes by reducing the activity of the enzyme TGase-K which catalyses the development of the corneal cell envelope (the final stage of keratinocyte differentiation).

• Use of Vitamin D3 analogues: they act on the multiplication and maturation of keratinocytes, although their mechanism is not yet known;

• Combination of dermocorticoids and vitamin D3 analogues: This combination is very effective, it is used in daily application for the first month, followed by a maintenance treatment at a rate of weekly applications over the weekend to prevent relapses.

• Use of 10% Salicylic Acid, a keratolytic agent, to thin the superficial layer of the epidermis (stratum corneum) by dissolving it.

Phototherapy also allows for the treatment of scalp psoriasis. It includes two modes, namely UVB phototherapy and PUVA therapy.

For severe cases, a systemic treatment based on Ciclosporin, retinoids or methotrexate may be suggested by the dermatologist. This type of treatment is necessary when the hair follicles are permanently damaged by the disease.

In addition to the various existing treatments, there are also some simple actions that can help to lessen the impact of scalp psoriasis on daily life:

• Use of gentle shampoo;

• Natural hair drying or adjusting the temperature to cool or lukewarm when using a hairdryer;

• Avoid tight and tied hairstyles (braids, ponytails, etc.);

• For hair colouring, delay the dyeing or highlighting process during flare-ups.

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SAURAT J. & al. Psoriasis. Dermatologie et infections sexuellement transmissibles (2016).

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