Allergic contact dermatitis after isotretinoin treatment for acne

Editor A 27-year-old man presented with an intermittent peri-orbital eczema. He had a history of asthma and a family history of eczema. He was on l-thyroxine, 100 µg daily, for hypothyroidism. He had no ocular conditions and denied using ophthalmic preparations. The patient noticed his skin had become generally drier since completing a course of systemic isotretinoin for acne vulgaris 1 year previously. Various moisturisers used by the patient included emulsifying ointment BP, aqueous cream BP and liquid paraffin 50%/white soft paraffin 50%. Oilatum Plus® and emulsifying ointment BP were used as soap substitutes. Active treatments included the once daily application of Daktacort® cream and subsequently Hydrocortisyl® 1% cream. On further review, the eczema had spread and active treatment was changed from Hydrocortisyl® cream to Protopic® 0.1% ointment with no clinical response. Patch testing to the British standard series, medicament series and the patient's own toiletries and emollients revealed positive (+) reactions to cetyl stearyl alcohol, benzalkonium chloride, phenylmercuric acetate and chlorhexidine digluconate. Cetyl stearyl alcohol (CSA) and benzalkonium chloride (BC) were of current clinical relevance (aqueous cream BP, emulsifying ointment BP, Hydrocortisyl® cream and Oilatum Plus®, respectively). No history of exposure to phenylmercuric acetate or chlorhexidine digluconate was noted. All topical medications were stopped excluding liquid paraffin 50%/white soft paraffin 50% and the patients eczema resolved. Allergies to BC or CSA are well recognized.1 It is exceptional to be allergic to both. On review of 734 patients patch tested in our department over a 6-year period, only 2 patients (< 0.2%) had a combined allergy to both compounds. This patient's contact dermatitis developed following the application of emollients to treat xerosis caused by isotretinoin therapy in an atopic individual. Topical and systemic retinoids affect both the structure and function of the epidermis. Sebum production is inhibited by retinoids and associated with increased transepidermal water loss from epidermis. Retinoids cause loss of tonofilaments and hemidesmosomes from epidermal cells resulting in increased epidermal fragility.2–4 Topical retinoids replenish Langerhans cell (LC) density in chronically sun-exposed human skin and also up-regulate their function as antigen-presenting cells. Systemic retinoids increase LC density in the epidermis of renal transplant patients. LCs are the primary antigen-presenting cells in the sensitization phase of contact hypersensitivity responses, and therefore, retinoids possibly modulate contact allergic reactions by immunologic means.5–7 Patients receiving systemic retinoids therefore frequently develop xerosis with consequent impaired barrier function. Frequent use of emollients in the presence of increased numbers of up-regulated LCs may predispose to allergic contact dermatitis. There are reports of contact allergic dermatitis to topical isoretinoin and a report of rubber glove dermatitis during isotretinoin treatment.8,9 It is prudent to patch test patients treated with retinoids who develop persistent eczema. BC and CSA are collectively almost ubiquitous in a wide array of creams and lotions. It is practical to provide patients diagnosed with these allergies with a list of safe preparations to use, as opposed to an exhaustive list of preparations that they should avoid. Liquid paraffin 50%/white paraffin 50% as shown is a suitable emollient. Advise patients that soap substitutes advertised with antiseptic properties often contain BC. Topical corticosteroids should be prescribed as ointment preparations, as most creams contain CSA. On review of 44 topical steroid preparations authorized by the Irish Medicines Board,10 23 contained CSA with the majority (n= 21) cream preparations. The exceptions were Fucidin H® ointment and Bettamousse® scalp preparation. Systemic isotretinoin therapy with ongoing xerosis of skin leads to impaired skin barrier function. Allergic contact dermatitis as a reason for persisting eczema should be considered and patch testing carried out.