Explain allergic contact dermatitis and patch testing to a parent — OSCE

Candidate instructions

You are the paediatric registrar. You have five minutes to speak with Mrs Chen, whose nine-year-old daughter Mia has atopic eczema that is otherwise well controlled, but has developed an intensely itchy, recurring rash around her umbilicus that comes back whenever she wears her favourite jeans. You suspect allergic contact dermatitis to nickel and are planning a patch test. Mrs Chen is worried that the usual creams have stopped working and that her daughter has developed a new allergy. Explain what allergic contact dermatitis is in plain language, why the usual creams have not worked, what the patch test involves, and the plan for avoidance and treatment — honestly and without overpromising. Answer her questions, check her understanding, and agree a plan with her. [3]

Actor brief (parent — Mrs Chen)

You are anxious and a little frustrated because the creams that used to work for Mia's eczema no longer help this rash around her navel, and she is scratching at school and missing sleep. You want to know: (1) Why have her usual creams stopped working — has her eczema got worse? (2) What is this nickel allergy, and how did she get it? (3) What is a patch test, and will it hurt or make her worse? (4) Will she have to give up wearing her favourite jeans forever? (5) Is this the start of lots of allergies? Push back if the candidate uses jargon, dismisses your worry, or overpromises that everything will simply go away. You calm when you feel heard and given honest, clear information. [3]

Exemplar candidate approach

Open and acknowledge. "Mrs Chen, please sit down. I can hear how frustrating this has been — watching Mia itch and lose sleep, and feeling that the creams that used to work are letting her down. The good news is that I think I know what is going on, and it is very treatable. Let me explain clearly, and please stop me with any question at all." [3]

Explain why the usual creams have not worked. "The reason the usual eczema creams have not helped this particular rash is that I do not think this is a simple flare of Mia's eczema. This looks like a different thing sitting on top of her eczema — a contact allergy, where her skin is reacting to something that touches it. The creams calm inflammation but they cannot switch off a reaction that keeps being re-triggered every time the trigger touches the skin, which is why the rash keeps coming back when she wears her jeans. Her eczema elsewhere is still well controlled, which is reassuring." [3]

Explain the diagnosis and how she got it. "Allergic contact dermatitis is when the skin's immune system has become sensitive to a particular substance — in Mia's case, almost certainly the nickel in the metal button of her jeans. It is a delayed reaction, so the rash appears a day or two after contact rather than straight away, which is why it took a while to connect it to the jeans. She became sensitised at some point in the past without anyone knowing, and now each time nickel touches her skin the rash flares. It is not dangerous, and it is nothing you or she did wrong." [2] [3]

Explain the patch test honestly. "A patch test is how we confirm it. We stick small chambers of common allergens, including nickel, onto her upper back under tape, leave them for two days, take them off, and then read the skin at three to four days and again at a week. It does not involve needles and it does not make her eczema worse, though a positive spot will show a small patch of the same rash, which is exactly the information we need. It tells us precisely what to avoid." [1]

Address the jeans and the future. "I want to be honest with you. If nickel is confirmed, Mia will need to avoid nickel-releasing items to keep this rash away — covering or replacing the jeans button, choosing nickel-free jewellery and buckles, and learning to read labels. That is very achievable, and most children's skin clears completely once they avoid the trigger. It does not mean she is going to develop lots of other allergies; it is one specific sensitisation, and many children grow up managing it easily." [2]

Check understanding and agree a plan. "Can I check — what is your biggest worry right now, and has anything I have said been unclear? Here is the plan: we book the patch test, I give you a mild cream to settle the current rash, we start a fragrance-free moisturiser, and once we know the result I will give you a written card listing what to avoid. Mia can absolutely keep going to school and her usual activities, and we will sort this out together." [3]

Mark scheme (10 marks)

• Empathy and relationship (2): acknowledges frustration and lost sleep, sits and listens, plain language, does not dismiss or overpromise. [3]
• Explains why the usual creams have failed (2): a contact allergy sitting on top of well-controlled eczema, re-triggered by contact, not a worsening of her eczema. [3]
• Explains the diagnosis and its origin (2): delayed type IV reaction to nickel, sensitised unknowingly, nothing the parent did wrong. [2] [3]
• Explains the patch test honestly (2): chambers on the back for two days, read at three to four days and a week, no needles, does not worsen eczema. [1]
• Checks understanding and agrees a plan (2): addresses the jeans and future-allergy worry honestly, invites questions, sets out next steps and ongoing availability. [3]