Dermatology · contact allergy · London
Patch test for contact allergies, the standard 5-day dermatology test for delayed-type contact hypersensitivity.
A patch test applies allergen panels to the skin under occlusion for 48 hours, with reads at day 2 and day 4-5. The standard investigation for delayed-type contact hypersensitivity — commonly nickel, fragrance, preservatives, hair dyes and cosmetic ingredients.
Why patients choose us
- 01
The right hands
We route you to a consultant dermatologist who runs contact-allergy clinics — the person applying and reading the panels is the person interpreting your result.
- 02
A full 5-day pathway
Apply on day 1, remove and read at 48 hours, final read at day 4-5 — with a written avoidance plan the same visit.
- 03
Independent, and free
We are paid by no clinic, so the recommendation is impartial and costs you nothing.
Key facts
Patch testing, in six lines.
The essentials of what patch testing is, what is applied, how long it takes, and who reads it.
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What it is
The standard dermatology test for delayed-type (Type IV) contact hypersensitivity.
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What is applied
TRUE-test or European baseline series, with extended panels (cosmetic, hairdressing, metal, medicament) as indicated.
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How long it takes
A 5-day process — apply, 48-hour occlusion, first read, then a delayed read at day 4-5.
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Who interprets it
A consultant dermatologist reads each patch against clinical relevance.
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How it complements prick tests
Prick testing tests immediate (IgE) hypersensitivity — patch testing tests delayed cell-mediated reactions. Different diseases, different tests.
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What you leave with
A written allergen-avoidance plan — with product substitutions and, where relevant, occupational advice.
Indicative pricing
What a private patch test costs in London.
Indicative ranges across our partner clinics. Send the details and we quote firm figures across two or three options.
In short
A standard European baseline patch test in our network: £450–£700, with the final read on day 5.
| Panel | Indicative range | Visits | Result |
|---|---|---|---|
| Standard patch test — European baseline series | £450–£700 | 3 visits | Day 5 |
| Baseline + cosmetic / fragrance extended panels | £600–£900 | 3 visits | Day 5 |
| Baseline + hairdressing / occupational panels | £650–£950 | 3 visits | Day 5 |
| Baseline + metal implant / dental panel | £700–£1,000 | 3 visits | Day 5 |
| Comprehensive series (baseline + 3+ extended panels) | £850–£1,300 | 3 visits | Day 5 |
| Patient-supplied products (own cosmetics tested) | £100–£250 | Add-on | Day 5 |
Prices vary by clinic, by which extended panels are added, and by whether your own products are tested alongside the standard series. We come back with a firm quote within one working day.
The problem
A patch test is only as good as who applies and reads it.
The panels tell you what the skin has reacted to — the dermatologist tells you which of those reactions actually matter for the dermatitis you came in with. We route you to a consultant with a contact-allergy clinic, not a general dermatology slot.
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Chronic hand or facial dermatitis?
We arrange baseline plus targeted extended panels and interpret against your cosmetics and workplace.
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Suspected cosmetic allergy?
We test your own products alongside the standard fragrance and preservative screens.
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Occupational dermatitis at work?
We add bespoke occupational panels and, if positive, issue an employer letter.
The 5 days
From application to report — what happens, in order.
One consultant from application to final read — no handoffs.
Phase 1 · Before
Consult and prepare
Phase 2 · During the 5 days
Apply, first read, final read
Phase 3 · After
Interpretation and plan
- 01
Before
Dermatology consultation
A confidential form and short consultation. History of the rash, occupational exposures, cosmetics and topical medications.
- 02
Before
Stop topical steroids on the back for 7 days
Steroids on the test site can suppress a true reaction. We give you the exact stop-date before applying panels.
- 03
During
Day 1 — panels applied to the upper back
Chambers of standard and extended allergens are taped to the upper back and left in place under occlusion.
- 04
During
Day 3 — patches removed, first read
Patches come off at 48 hours. A first read is taken 20-30 minutes later, once irritation from the tape has settled.
- 05
During
Day 5 — final read and interpretation
The delayed read at 96-120 hours is the one that matters — most true positives appear here, not at day 3.
- 06
After
Occupational and cosmetic review
Each positive is cross-checked against your work, your cosmetics and your medications for clinical relevance.
- 07
After
Written plan with avoidance guidance
You leave with a printed allergen-avoidance sheet, product substitutions, and an occupational letter if needed.
End-to-end: 5 days, three short clinic visits. Written plan: final visit.
What it shows
The commonest patch-test positives.
Patch testing answers a specific question — which chemicals your skin has become sensitised to. These are the positives we see most often.
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Nickel (jewellery, buttons)
The single commonest positive on patch testing — earrings, watches, jean buttons, coins.
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Fragrance mix
Screens for the most frequent perfume-derived cosmetic allergens.
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Preservatives (MI, formaldehyde)
Methylisothiazolinone, formaldehyde releasers — the current epidemic in leave-on cosmetics and wet wipes.
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Hair-dye (PPD)
Para-phenylenediamine — hairdresser and client hand and scalp dermatitis.
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Rubber accelerators
Thiurams and carbamates in gloves, elastic and footwear — a common occupational finding.
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Cosmetic ingredients
Extended panels test your own products against known cosmetic allergens.
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Metal implant reactions
Dental, orthopaedic or cardiac implant hypersensitivity work-up — requires specialist interpretation.
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Red flag: severe blistering reaction — urgent dermatology, systemic steroid
A widespread bullous reaction at a patch site needs same-day dermatology review and, sometimes, systemic steroid.
Panels
Not all patch-test panels are the same.
What each series on the referral actually screens for.
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European baseline series
The standard ~30-allergen screening panel — nickel, fragrance mix, preservatives, rubber, medicaments.
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TRUE-test
A ready-to-apply thin-layer version of the baseline series, used where a rapid standard screen is enough.
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Cosmetic / fragrance panel
Extended fragrance chemicals, sunscreen filters and cosmetic vehicles — for facial and periocular dermatitis.
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Hairdressing panel
PPD-related dyes, bleaches, permanent-wave chemicals — for scalp, hand and salon-worker dermatitis.
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Medicament panel
Topical antibiotics, anaesthetics and corticosteroids — for chronic ulcer or eczema patients on multiple creams.
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Metal implant / dental panel
Extended metal series for pre-operative or post-implant hypersensitivity assessment.
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Occupational bespoke panels
Custom panels for construction, healthcare, food-handling and manufacturing exposures.
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Patient-supplied products
Your own leave-on cosmetics or occupational chemicals tested alongside the standard panels.
If a positive is found
Management after a clinically relevant positive.
Every positive triggers a specific plan — the dermatologist decides which of the following apply.
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Allergen-avoidance advice
The core intervention — the written list of chemicals to avoid and safe alternatives.
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Emollient regimen
Fragrance-free, preservative-light emollients to restore the barrier during recovery.
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Topical corticosteroids
A short course of a mid-potency steroid to settle active contact dermatitis.
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Occupational-health plan
A letter for your employer or occupational-health team, with substitution advice.
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Cosmetic ingredient checking
A shortlist of tested-safe brands and an ingredient app to keep with you.
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Metal implant review
Onward orthopaedic or dental referral where a metal positive is clinically relevant.
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Systemic immunosuppression
Reserved for chronic severe dermatitis unresponsive to avoidance and topicals.
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Structured dermatology follow-up
Review at 6-8 weeks to confirm avoidance is working and adjust the plan.
Our vetted London network
A small panel of clinics, we picked them.
Contact-allergy clinics across central, north, west and south London. Not listed publicly — introductions are made privately, once we understand your case.
Selection criteria
How we choose every clinic in our network.
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Consultant dermatologists with a contact-allergy subspecialty clinic
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European Society of Contact Dermatitis / BSCA-aligned protocols
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Standardised International Contact Dermatitis Research Group scoring
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Written avoidance plan and occupational letter issued at the final read
Safety and eligibility
One of the safest tests in dermatology.
Patch testing is exceptionally safe — the practical points are the pre-test steroid stop, keeping the back dry, and knowing which reactions still need urgent review.
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Painless application
Adhesive chambers on the upper back — no needles, no scratching, no injections.
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Keep the back dry
No showers, swimming or heavy exercise while the patches are on — sweat lifts the panels off.
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No sun or UV on the back
UV suppresses reactions — avoid sunbeds and prolonged sun exposure for the 5-day window and 2 weeks beforehand.
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Stop topical steroids 7 days ahead
On the test site only. Systemic steroids above 10 mg prednisolone should ideally be paused — discuss first.
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Angry back reaction is a limit
If many allergens flare at once, the whole back becomes irritable — some results are then non-interpretable and the test may need repeating.
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A negative test is not a full clear
Patch testing tests delayed hypersensitivity — not immediate urticaria, not food allergy, not airborne triggers.
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Not for immediate reactions
Latex urticaria, hives from food or drugs — those need prick or specific-IgE tests, not patches.
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Late reactions can appear at day 7
Metal and corticosteroid allergens sometimes read at 7 days — we will ask you to photograph and report any late change.
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Bring every product you use
Cosmetics, shampoos, work chemicals, gloves — the ones that touch your skin are the ones that matter for interpretation.
Red flags — when to escalate
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Angry back reaction — widespread irritability across the test site
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History of Stevens-Johnson syndrome — patch testing must be individualised
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History of DRESS syndrome — specialist-only testing, often deferred
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Occupational dermatitis affecting livelihood — urgent occupational-health input
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Metal implant hypersensitivity — pre- or post-op assessment by specialist
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Cosmetic allergy with airborne / periocular exposure — extended aerosolised panel
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Latex contact urticaria — immediate reaction, needs prick / specific-IgE testing instead
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Systemic contact dermatitis — a positive allergen ingested or inhaled — dermatology review
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Post-implant chronic urticaria — differential includes non-contact mechanisms
Reading your report
A patch-test report can look intimidating. It isn’t.
Whatever the finding, the report keeps to the same four parts.
A quiet reminder
The report is written for your doctor, not for you — and that’s normal.
If you would like us to talk you through it before your follow-up, just ask.
- 01 Header
History and suspected allergens
Your presenting dermatitis, occupational and cosmetic exposures, and the panels applied.
- 02 Technique
Panels and reading schedule
Which series were used, the day-3 and day-5 reading times, and the ICDRG grading applied.
- 03 Findings
Allergen-by-allergen result and grade
Each chamber graded from negative through +, ++, +++ or irritant, with the day of reading noted.
- 04 Impression
Clinical relevance and next step
Which positives explain your dermatitis, the avoidance plan, and any onward occupational referral.
Sources
The bodies that set the standards.
Reviewed on 2026-07-30. Next review by 2027-07-30. Reviewed by Pulse Atlas Editorial Board ().
- British Society for Cutaneous Allergy — patch testing standards and allergen series.
- European Society of Contact Dermatitis — European baseline series and guidelines.
- British Association of Dermatologists — contact dermatitis patient information.
- American Contact Dermatitis Society — allergen of the year and clinical resources.
Recognised by major UK insurers
Cover depends on your policy and clinic; we confirm with your insurer before booking.
Frequently asked
Everything we get asked about patch testing.
Quick answers on cost, referrals, prick-vs-patch, the 5-day schedule, and what happens if a positive is found.
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What does patch testing show?
Delayed-type (Type IV) contact hypersensitivity — the cell-mediated allergy that causes contact dermatitis. Common positives include nickel, fragrance, preservatives, hair dye and rubber accelerators.
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How is patch testing different from a prick test?
A prick test detects immediate (IgE) allergy — the hives-and-anaphylaxis kind, read within 20 minutes. Patch testing detects delayed cell-mediated allergy — the eczematous contact-dermatitis kind, read at 48 and 96-120 hours. Different tests for different diseases.
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Why is it a 5-day process?
Delayed hypersensitivity takes 48-96 hours to appear on the skin. Panels are applied on day 1, removed and first-read at day 3 (48 hours), and finally read at day 5 — most true positives only show at that delayed read.
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Does patch testing hurt?
No. Adhesive chambers are taped to the upper back — no needles. Any discomfort is usually itch at the site of a true positive reaction while the panels are on.
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Can I shower during the test?
No — the back must stay dry for the 48 hours the patches are in place. After removal, keep the marked test grid visible until the final read on day 5.
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When should I stop my creams before the test?
Topical steroids on the upper back should stop 7 days before applying panels. Emollients on the back should stop 24 hours before. Do not stop your usual medications elsewhere without checking.
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What if my back reacts to everything?
A so-called angry back reaction — the whole test site becomes irritable — can render results uninterpretable. The dermatologist may repeat testing with fewer allergens, spread across sessions.
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How much does private patch testing cost in London?
A standard European baseline series is typically £450–£700 in our network. Adding cosmetic, hairdressing or metal implant panels raises the cost. We confirm a firm figure within one working day.
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Do I need a referral?
Most clinics accept self-referral for patch testing. We can arrange a fast-track private GP or dermatology referral if your insurer requires one.
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What happens if a positive is found?
The dermatologist writes an avoidance plan — which cosmetics and materials to avoid, safer alternatives, and, if the dermatitis is occupational, a letter for your employer or occupational-health team.
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In practice, in London
Booking patch test for contact allergies privately in London — what actually happens
With patch test for contact allergies, the London question is usually about report turnaround and the radiologist reading it — not whether the scan is available. On the NHS, patch test for contact allergies typically sits behind a triage step and a wait that can stretch from a few weeks into months. In London’s private sector, the same appointment often lands within days. That speed matters when symptoms are disrupting work, sleep, or a plan you’d already committed to — and it’s the single most common reason people call us in the first place.
In practice, a private patch test for contact allergies appointment in London means a named consultant, a proper hour in the room (or the equivalent on a video call), and a report you can actually read. Most of the imaging suites and endoscopy units we use sit within a mile of Harley Street or in Chelsea and Fulham, and turnaround on findings is measured in days, not weeks. For patch test for contact allergies specifically, the difference between a routine report and a sub-speciality read is where private care earns its keep.
There are a lot of consultants in London who can technically handle patch test for contact allergies. Fewer who do it week in, week out for the exact question you’re bringing. We spend most of our time working out which is which — and being straight when a different test or a different specialist would serve you better. Everything runs to CQC, GMC and Royal College standards; the choice is about fit, not floor.
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