Irritant and allergic contact dermatitis

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Map work and home activities hour by hour. Repeated water, detergent and glove use commonly create irritant disease, especially on finger webs and backs. Allergic patterns depend on where a sensitiser travels: eyelids from transferred nail product, face from fragrance or airborne resin, feet from shoe chemicals and hands from preservatives or rubber accelerators.

Management begins before formal testing by reducing damaging exposure, substituting cleansers and protecting skin without creating excessive occlusion. Patch testing is valuable for persistent, occupational, facial or treatment-resistant disease. Bring products and exact ingredient data; standard series alone may miss workplace allergens.

Irritant and allergic contact dermatitis care should combine visible inflammation with itch, pain, sleep, occupation and treatment burden. Agree where each product goes, how much is used and when response will be reviewed; explain urgent features separately so normal fluctuation is not confused with infection or treatment failure.

Key points

Irritant dermatitis reflects exposure dose and barrier damage; allergic contact dermatitis is delayed type IV hypersensitivity requiring previous sensitisation.
Wet work means repeated hand wetting or prolonged glove occlusion as well as obvious chemical exposure; atopic skin lowers the irritant threshold.
Allergic dermatitis can spread beyond the exact contact border, while irritant disease often affects the most exposed surfaces, but morphology alone is not definitive.
Patch testing assesses delayed contact allergy; skin-prick testing and serum specific IgE do not diagnose allergic contact dermatitis.
Ask for product ingredient lists, safety-data sheets, glove composition, tasks, hobbies and improvement away from exposure before giving avoidance advice.
A positive patch test identifies sensitisation; clinical relevance requires a real exposure and a compatible site and time course.
For Irritant and allergic contact dermatitis, document body sites, severity, sleep and function, recent treatment, infection features and what the patient can realistically apply each day.
In Irritant and allergic contact dermatitis, reassess the diagnosis when a well-used, correctly potent regimen fails rather than repeatedly intensifying treatment without examining adherence, exposure and mimics.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Cumulative irritant exposure

Water, detergents, solvents, friction, occlusion and repeated hand cleansing directly damage barrier; dose, duration and background atopy determine the threshold.

Delayed contact sensitisation

Small chemicals penetrate skin, bind proteins and prime antigen-specific T cells, causing allergic dermatitis on later exposure to metals, preservatives, fragrances, rubber and many other allergens.

Airborne and photo-contact exposure

Plant, resin, spray and sunscreen allergens may reach exposed skin through air or require light activation, producing distributions beyond direct hand contact.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Irritant barrier injury
Lipid extraction and keratinocyte damage increase water loss and inflammatory signalling without requiring immune memory, so anyone can react above a sufficient exposure dose.
2
Sensitisation phase
Antigen-presenting cells carry a new contact allergen to lymph nodes where allergen-specific T-cell memory develops without necessarily causing a visible first eruption.
3
Elicitation phase
Re-exposure activates resident and circulating T cells over hours to days, creating itch, vesiculation, oedema and eczema that can extend beyond contact borders.
4
Chronic lichenification
Ongoing exposure plus rubbing thickens skin, deepens fissures and obscures the original geometry, allowing irritant and allergic mechanisms to coexist.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Irritant exposure geometry

Dryness, burning, fissures and eczema concentrate on repeatedly wet or chemically exposed surfaces and often improve during sustained time away.

Delayed allergic spread

Itchy vesicular or oedematous eczema appears hours to days after exposure and may extend beyond the contact boundary.

Eyelid and facial clue

Thin-site dermatitis from transferred nail, hair, fragrance, preservative or airborne allergens may occur with relatively spared hands.

Occupational chronology

Improvement on holiday and recurrence after specific tasks supports workplace causation, although delayed recovery can obscure a weekend relationship.

Immediate-reaction departureRed flag

Wheals, respiratory symptoms or collapse within minutes suggests contact urticaria or anaphylaxis and requires an immediate-allergy pathway.

Red flags requiring action

Eye involvement, deep chemical injury, widespread bullae, fever, rapidly progressive pain, occupational inability to avoid exposure or persistent facial and hand disease requires urgent or specialist assessment.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Task and product exposure inventoryFirst step
Why
Identify irritant dose, plausible sensitiser and opportunities for substitution.
Interpretation and limitations
Use exact ingredient and safety-data names; marketing labels such as natural, hypoallergenic or fragrance-free do not exclude relevant chemicals.
02
Delayed patch testing
Why
Detect contact sensitisation in persistent or high-impact eczema.
Interpretation and limitations
Allergens remain under occlusion with readings on separate days; positive morphology and strength require interpretation against current and past exposure.
03
Mycology from active scale
Why
Exclude dermatophyte infection in unilateral or annular hand and foot disease.
Interpretation and limitations
A negative sample is conditional on adequate untreated edge material; steroid exposure can create tinea incognito.
04
Skin-prick or specific IgE only for immediate symptoms
Why
Assess rapid contact urticaria or respiratory allergy when the history supports it.
Interpretation and limitations
These tests show sensitisation and do not diagnose delayed allergic contact dermatitis; systemic-risk testing belongs in specialist care.
05
Occupational health assessment
Why
Link exposure control with safe work participation and statutory reporting where applicable.
Interpretation and limitations
Job title alone is insufficient; observe tasks, wet-work duration, glove changes and availability of safer alternatives.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Atopic hand eczema

Personal atopy, diffuse dryness and childhood flexural disease support background susceptibility, but do not exclude superimposed occupational irritant or allergic exposure.

Tinea manuum

Unilateral palmar scale with tinea pedis or an active border suggests dermatophyte infection and should be sampled before escalating corticosteroid.

Psoriasis

Sharply demarcated plaques, nail pits, extensor disease and hyperkeratotic fissures may mimic chronic contact dermatitis on hands and feet.

Protein contact urticaria

Immediate itching, wheals and sometimes systemic symptoms after food or latex exposure represent an IgE-mediated pattern distinct from delayed eczematous allergy.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Likely irritant diseaseReduce cumulative barrier damageFirst stepExposure is frequent and dose-related, patchy on contact surfaces and lacks a specific delayed allergen pattern.

1Substitute soap and harsh cleanser with a suitable emollient wash, reduce wet-work duration and use task-specific gloves with cotton liners when prolonged wear is unavoidable.
2Apply leave-on emollient repeatedly and a site-appropriate topical corticosteroid to active inflammation for a defined course.
3Review actual workplace implementation, fissure healing and time away; investigate allergy or tinea if response remains incomplete.

02Possible allergic contact diseaseTest and establish relevanceDermatitis persists, spreads, involves face or eyelids, follows a specific product or threatens occupation.

1Refer for patch testing with baseline and occupation- or product-specific allergens, supplying ingredient lists and representative products as requested.
2Interpret each positive reaction as current, past or unknown relevance before recommending avoidance and chemically suitable substitutes.
3Provide written synonym and product advice and coordinate occupational health so protection is achievable without unnecessary exclusion.

03Acute severe exposureDecontaminate and assess injuryA corrosive chemical, eye exposure, extensive oedema, blistering or systemic reaction occurs.

1Remove contaminated clothing and irrigate according to chemical guidance while protecting staff, then seek emergency toxicology or burns advice.
2Assess eyes, airway, body surface and systemic physiology; do not neutralise chemicals unless a specific protocol directs it.
3DefinitiveDocument substance, concentration, duration, first aid and workplace circumstances for definitive care and prevention.

Key medicines and prescribing safety2 treatments · regimens, roles and cautions

A mild anti-inflammatory option for selected thin or sensitive sites after active chemical injury and untreated infection have been excluded.

Hydrocortisone 1% cream

Adults apply thinly once or twice daily for no more than seven days under this licence, with site-specific clinician review if further treatment is needed.

Avoid eyes, broken chemical burns, infection and prolonged face or flexure use; excipients themselves can irritate or sensitise and persistent disease needs exposure reassessment.

A potent topical corticosteroid for thicker or more inflamed contact dermatitis when exposure control and emollient care are also addressed.

Betamethasone valerate 0.1% cream

Apply a thin layer once or twice daily to affected trunk, limb or hand skin for up to four weeks, then reduce or stop with control.

Avoid thin sites, untreated infection, large areas and occlusion unless prescribed; monitor atrophy and systemic absorption and do not let suppression conceal continued workplace exposure.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Chronic occupational disability

Persistent fissuring and pain can prevent hand hygiene, glove use, clinical work, food preparation or manual tasks and may threaten employment.

Secondary infection

Barrier disruption permits bacterial or viral infection, with increasing pain, pustules, crust, spreading erythema or systemic illness changing urgency.

Generalised autoeczematisation

A severe local dermatitis can provoke distant symmetrical eczema, making distribution appear unrelated to the original contact site.

Avoidance-related harm

Over-broad allergen lists and unsuitable glove advice can create unnecessary work restriction while hidden synonym exposure continues.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Track hand-washing episodes, glove hours, product substitution, days away from work, fissure pain and topical-treatment use.
After patch testing, check that the named allergen is absent from replacement products and that dermatitis improves with genuine avoidance.
Review occupational function and involve workplace services early when recommended controls cannot be implemented.
At review of Irritant and allergic contact dermatitis, compare itch, sleep, fissuring or ooze, affected sites, function and treatment use with the agreed baseline.
For Irritant and allergic contact dermatitis, record adverse effects, new contact exposures and the safety-net for pain, fever, rapidly spreading disease, eye symptoms or systemic illness.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Dose distinguishes irritancy

A substance need not be intrinsically harsh when repeated water, friction and occlusion cumulatively exceed the skin barrier’s capacity.

Allergy can cross borders

Activated T cells create eczema beyond the exact contact print, so a diffuse margin does not exclude contact allergy.

Eyelids receive transferred products

Hand-applied nail, hair and fragrance allergens can produce striking eyelid eczema while the thicker palms look normal.

Positive is not relevant by default

Patch-test sensitisation from a remote exposure should not drive current restriction unless ingredient and distribution align.

Gloves can help or harm

Wrong material permits chemical penetration, while sweat and prolonged occlusion worsen irritant disease and rubber additives can sensitise.

11Common pitfallsFrequent interpretation and management errors.

01
Calling every occupational hand rash allergic and omitting wet-work dose reduction.
02
Using skin-prick tests to investigate delayed eczematous contact reactions.
03
Giving a generic wear gloves instruction without specifying material, task duration or cotton liners.
04
Ignoring ingredients in prescribed topical treatments as possible allergens in worsening dermatitis.
05
Applying corticosteroid while the corrosive chemical remains on skin instead of urgent decontamination.