Severe childhood eczema, a private IgG panel, and a child losing weight

The IgG panel is uninterpretable and should not drive management.

• Food-specific IgG (including IgG4) reflects exposure and the development of immunological tolerance, not allergy. Most children who eat milk, egg, wheat and peanut will have detectable IgG to them; a positive result in a child who eats the food without immediate symptoms is the expected normal finding.
• All major allergy bodies advise against IgG testing for the diagnosis of food allergy; it generates false positives and, as here, unnecessary elimination.
• The clinical evidence in this boy supports that: three weeks of milk and wheat exclusion with no change in the eczema.

What I advise

1. Reinstate milk and wheat, with dietetic support and in graded amounts, because there is no evidence of immediate or delayed reactions to them and his growth is already faltering.
2. Do not restrict peanut on the basis of an IgG result alone. Peanut is worth a careful history (has he ever eaten it? any immediate symptoms?) - if there is a genuine immediate-type history, skin prick testing or specific IgE is indicated; if he eats peanut without symptoms, no test and no restriction.
3. Explain that food allergy does occur in atopic dermatitis but usually as immediate reactions to a small number of foods (egg, milk, peanut) in infants, and that delayed eczematous flares attributed to food are rarely confirmed on double-blind challenge.
4. Emphasise the harm already accruing: a child on a restricted diet with a 41-centile drop in weight and food refusal is being damaged by a test that has no diagnostic value.
5. Refer to a paediatric dietitian the same week, involve the health visitor, and document the conversation and the reasoning in writing for the parents.

Step 1 - check the basics before escalating.

• Quantity and potency: a 4-year-old needs roughly 250–500 g of emollient per month and fingertip-unit-based topical steroid dosing. 'Twice a month' mometasone is under-treatment, not treatment failure.
• Technique, frequency and duration; whether flares are being treated for long enough (typically until the skin is smooth, not just less red).
• Secondary bacterial infection or eczema herpeticum - crusting, pustules, pain, fever or rapidly worsening monomorphic lesions.
• Trigger review: soap, bubble bath, woollen clothing, overheating at night; sleep and quality of life for the whole family.

Step 2 - address steroid phobia explicitly, because it is the main barrier.

• Name it, explain the difference between potency, site and duration, and give a written plan with how much, where, and for how long.
• Explain that atrophy risk comes from unsupervised long-term potent steroid use on thin skin, not from correctly used mometasone on the trunk and limbs for 1–2 weeks at a time; untreated severe eczema causes skin damage, sleep loss and growth impairment.
• Offer a topical calcineurin inhibitor for the face/eyelids if steroid-sparing is needed for the parents' confidence.

Step 3 - escalate. Wet-wrap therapy or a short course of intensive topical treatment first, then systemic therapy: dupilumab is licensed from 6 months in the UK/EU for severe atopic dermatitis and would be my first choice in a child with growth faltering; ciclosporin 2.5–5 mg/kg is a faster short-term alternative.

Before a systemic agent: FBC, U&E, LFTs, blood pressure, weight and height plotted, varicella and measles immunity/vaccination status, hepatitis B/C and HIV serology if a conventional immunosuppressant is planned, TB screening where relevant, and a clear discussion of live vaccines (give any due live vaccines before starting an immunosuppressant).

I would decline both requests, kindly and with reasons, and offer something concrete instead.

• I would explain that I cannot endorse a test I regard as invalid, and that writing a letter would make me complicit in a dietary restriction that is already harming his growth. I would say clearly that this is not a judgement about them as parents - they were sold a test by a laboratory, and their instinct to help their child was right.
• I would not repeat the IgG test. A repeat gives the same uninterpretable answer at a cost, and repeating it would imply the first result had meaning.
• What I would offer: a joint appointment with the paediatric dietitian and the health visitor, a written eczema treatment plan, an explicit safety-net about food refusal and weight loss, and a review date. I would also write to the GP so that the plan is shared and so no one reintroduces the exclusion by default.
• I would check whether the parents' anxiety is driven by fear of anaphylaxis, and if so address that specifically - an allergy action plan and clear advice about what an immediate reaction looks like can be more reassuring than a test.

Documentation: the discussion, the reasoning, that the parents were given the choice to continue the exclusion against advice, the growth data, the referral, and the safety-net. If the weight continues to fall or the child becomes symptomatic from the restriction, the balance shifts from persuasion to child-protection processes - I would say that openly and early rather than as a threat, and involve the health visitor now.