Open Access
Feature Article

Scalp pruritus – scratching for answers

Open Access
Feature Article

Scalp pruritus – scratching for answers

SARAH ROSE ADAMSON, RACHAEL DAVENPORT, ALVIN H. CHONG, Peter Foley

Figures

© nobeastsofierce/ shutterstock.com
© nobeastsofierce/ shutterstock.com
Dr Adamson is a Dermatology Research and Education Fellow at the Skin Health Institute, Melbourne; and a Dermatology Fellow at The Royal Women’s Hospital, Melbourne. Dr Davenport is a Dermatology Registrar at St Vincent’s Hospital, Melbourne. Adjunct Associate Professor Chong is a Specialist Dermatologist at St Vincent’s Hospital, Melbourne; Head of the Transplant Dermatology Clinic and Producer of Spot Diagnosis Podcast at Skin Health Institute, Melbourne. Associate Professor Foley is the Director of Research at the Skin Health Institute, Melbourne; Head of Dermatology Research at St Vincent’s Hospital, Melbourne; and Associate Professor of Dermatology at The University of Melbourne, Melbourne, Vic.

Treatment

Medicated shampoos may be effective for mild cases of scalp psoriasis. These preparations contain active ingredients such as tar and salicylic acid. For moderate to severe scalp psoriasis, topical corticosteroids are the mainstay of treatment. Potent and very potent topical corticosteroids are suitable for scalp psoriasis. Start with a topical corticosteroid lotion such as mometasone furoate 0.1% or methylprednisolone aceponate 0.1%; these can be applied to the scalp after shampooing and left overnight. Topical corticosteroid treatment is more efficacious when combined with calcipotriol, a vitamin D derivative.3 A combination product containing calcipotriol and betamethasone was available on PBS; however, it has recently been discontinued. Another treatment option is clobetasol propionate 0.05% shampoo, which is also available on the PBS for this indication. This is applied to the scalp for five to 15 minutes, then rinsed out, initially daily then once to twice a week for maintenance.

Patients with thickened plaques and adherent scale require a keratolytic preparation. This is usually left on overnight and washed out the next morning. A typical preparation may include a combination of a tar (e.g. 3 to 10% LPC) and salicylic acid 3 to 5% (maximum 10%) in aqueous cream, extemporaneously compounded.

In more severe cases, dithranol at a concentration of 0.1 to 0.2% can be added to compounded preparations for overnight application to the scalp. Higher concentrations of dithranol (0.5 to 1%) can be used for short contact treatment, applied and left for no more than 30 minutes before being washed off. Short-contact treatment can be very irritating to inflamed skin. Preparations containing dithranol and tars should be used with caution by fair-haired individuals as they can stain the hair. Dithranol’s propensity to cause red–brown staining and skin irritation has contributed to a decline in its use.

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Systemic therapy, such as methotrexate, acitretin, ciclosporin, or biologic therapy, can be used in patients with treatment-resistant scalp psoriasis. Methotrexate can be prescribed by GPs; however, other systemic therapies, such as ciclosporin, acitretin (except in Western Australia) and apremilast must be prescribed and managed by a dermatologist. Referral to a dermatologist is indicated when topical treatments and methotrexate (if the GP is comfortable prescribing this) are unable to provide adequate disease control and additional therapy is required.

Biologic therapy including tildrakizumab (IL-23 inhibitor), guselkumab (IL-23 inhibitor), risankizumab (IL-23A inhibitor), etanercept (TNF inhibitor), adalimumab (TNF-alpha inhibitor), infliximab (TNF-alpha inhibitor), secukinumab (IL-17A inhibitor), and ixekizumab (IL-17A inhibitor) be used in severe scalp and generalised psoriasis.4 Biologic therapy is PBS subsidised for severe, treatment resistant psoriasis and must be prescribed by a specialist dermatologist.

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Pediculosis capitis (head lice)

Clinical features

Infestation of the scalp by the head louse is common, especially in children. Infestation is typically acquired by direct head-to-head contact, after which the female louse lays eggs (nits) – usually five to 10 per day – cemented to the base of hair shafts. Viable eggs appear tan to brown, whereas empty eggs are clear to white. Nits are difficult to dislodge from hair shafts, distinguishing them from seborrhoeic scales and hair casts, which glide easily along the shaft. Clinically, patients with head lice present with itch that is prominent over the occipital and parietal scalp, where infestation tends to be greatest. Papules are occasionally observed (Figure 3a). There may be secondary impetiginisation and hairs matted down by exudates.