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A 33 year old woman presented with an intensely itchy, erythematous, blistering eruption bilaterally on the distal upper and lower limbs a week after coming back from a holiday in India. The rash was associated with oedema. She had attended a friend €™s wedding while in India, and as part of the festivities she took part in the ritual of €œmehndi, € which involved having an intricate henna design painted on her hands and feet. Five days after this ritual she developed a sharply demarcated erythematous, itchy, papulovesicular swelling in the proximal distribution of the tattoo design, which spread distally (figure). Other than the skin irritation, she had no other symptoms and was systemically well.

Questions

1 What is the diagnosis?
2 What investigations should be performed?
3 How is this condition managed?

Answers

1 What is the diagnosis?

Short answer

The diagnosis is contact dermatitis to paraphenylenediamine (PPD). This chemical is widely used in hair dye and is an ingredient in many other products, including black henna, which is used in temporary tattooing.

Long answer

PPD is an aromatic amine compound that is primarily used as a hair colouring agent. It is also found in a variety of products including textile dyes, photography development agents, certain local anaesthetics, cosmetics, and printing inks. It is becoming increasingly used in temporary tattoos as an addition to henna.

Henna is a greenish brown vegetable colouring from the leaves of the plant Lawsonia inermis or L alba, which grows in India, North Africa, and Sri Lanka. The active ingredient is lawsone (2-hydroxy-1,4-naphthoquinone). On its own, henna poses little risk of allergic contact dermatitis, but PPD is increasingly being added to make henna tattoos look more like real ones. The addition of PPD darkens the appearance of henna ( €œblack henna €); makes the staining effect last longer; and it allows quicker application, quicker drying (natural henna takes four to 12 hours), and greater definition to the lines of the tattoo. Because higher concentrations of PPD darken the henna paste, and because of the lack of rules governing the use of black henna, PPD is often used in much higher concentrations than in hair dye.

PPD causes allergic contact dermatitis in susceptible people. Whereas irritant contact dermatitis occurs in anyone who has prolonged contact with irritants €”such as acids, alkali, solvents, detergents, and friction €”allergic contact dermatitis occurs only in people with an allergy to the compound. Allergic contact dermatitis is a delayed-type hypersensitivity reaction (type IV hypersensitivity). There are four types of hypersensitivity reactions: type I, immediate-type IgE mediated reactions; type II, antibody mediated reactions; type III, immune complex deposition reactions; and type IV, T cell-mediated delayed-type reactions. The type IV reaction is an unwanted exaggerated response of a normal immune system after exposure to an allergenic compound, such as PPD. The foreign antigen is presented to T helper cells, which release cytokines that result in accumulation of macrophages and activation of cytotoxic T cells. It is this cascade of events that causes localised inflammation and damage. The reaction usually occurs 24-48 hours after exposure to the allergen, and the intensity and duration of the inflammatory reaction depend on the patient €™s sensitivity to the allergen and the concentration absorbed. Because high concentrations are often used, black henna has also been reported to provoke immediate antibody mediated type I hypersensitivity. Vesiculous or vesiculobullous reactions are most common, and they typically present as a painful, erythematous, oedematous, blistering eruption. Even if the reaction is treated, permanent scarring, keloid formation, post-inflammatory pigmentation changes, and life long sensitisation to PPD and its related compounds (box) can occur. Anaphylaxis and angioneurotic oedema have also been reported after use of black henna.

Products containing paraphenylenediamine (PPD) and PPD related compounds

Azo dyes

  • Semi-permanent and temporary hair dye, ink, petrol, diesel fuel, and some food colourings

Drugs

  • Benzocaine, carbutamide, hydrochlorothiazide, 4-aminobenzoic acid (antituberculous drug), 4-aminosalicylic acid, sulfonamides

Allergic contact dermatitis to PPD is an important problem, especially because €”unlike most other common allergens €”the incidence of reactions to PPD is rising. A recent six year retrospective study in a busy London dermatology department showed an upward linear trend of positive PPD patch test results in 6177 patients with suspected contact dermatitis. The authors postulated that this rise was caused by the increased use of permanent oxidative hair dye. No data are available on the prevalence of PPD sensitivity in the UK general population, but a study in Thailand in 2007 found a prevalence of 2.7% in the 2545 healthy volunteers who were patch tested.

2 What investigations should be performed?

Short answer

To confirm the diagnosis and identify any crossreactants, patch testing must be performed using one of the commercially available European standard series of allergens.

Long answer

Diagnosis of contact dermatitis to PPD is largely clinical. It is important to check the patient €™s occupational history (PPD is the chemical product most often responsible for eczematous reactions in hairdressers) and previous use of dyes or henna. Once the diagnosis is made it is useful to arrange patch testing to confirm the allergen responsible and to identify the severity of the reaction as well as potential crossreactants. PPD is included in the European standard series for diagnostic patch testing for patients with eczema. It is usually applied at a concentration of 1% mixed with petroleum, but even at this low dose it can elicit a vesiculobullous reaction. Because of this, in patients who have had a severe reaction, it should be applied at a concentration of 0.1%. Given that 1% PPD can have such a violent reaction in sensitised people, it is worrying that black henna being sold for body art in the United Arab Emirates was found to contain up to 29.5% PPD.

3 How is this condition managed?

Short answer

PPD contact dermatitis is managed with potent topical or oral corticosteroids as well as topical emollients. Advise patients to avoid the allergen and potential crossreactants.

Long answer

The mainstay of the management of contact dermatitis to PPD is the application of potent topical corticosteroid, typically clobetasol propionate 0.05% ointment twice daily or, particularly if the reaction affects the face, mometasone furoate 0.1% ointment. Mometasone furoate 0.1% is favoured because of its once daily application and appropriate dosage strength; however, betamethasone valearate 0.1% ointment would be an appropriate alternative. Potent steroids need be used for a short time only, such as five days, until the inflammation has settled, and then less potent compounds such as hydrocortisone ointment can be used. Topical corticosteroids should be used in conjunction with topical emollients such as liquid and white soft paraffin ointment, which should be applied frequently and generously. Antihistamines can help reduce associated pruritus. If the patient is systemically unwell, then a reducing regimen of oral corticosteroids could be started. Advise the patient to avoid the allergen and any potential crossreactants.

Patient outcome

Our patient was treated with a twice daily topical emollient (isopropyl myristate and liquid paraffin gel) and topical clobetasol propionate ointment 0.05% applied under an occlusive dressing. The topical corticosteroid was applied twice daily for two weeks, once daily for seven days, and then every other day for seven days. On completion of this course she had post-inflammatory hyperpigmentation. She was given the appropriate advice, including sun avoidance, and will be followed up in six months for consideration of further treatment if necessary.

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