Contact dermatitis (irritant and allergic) !
An itchy or burning rash from something touching the skin, by direct irritation (soaps, water, chemicals) or by allergy (nickel, rubber, fragrances).
Updated 2026-11-01
Structures involved
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In the clinical exam
Why it happens
- Innate and adaptive immunity: overview
- Keratinocytes, melanocytes, Langerhans and Merkel cells
- Skin: epidermis layers, dermis, hypodermis
What it is
Inflammation of the skin caused by an external substance. Irritant contact dermatitis is direct, non-immune damage; allergic contact dermatitis is a delayed (type IV) cell-mediated hypersensitivity in a previously sensitised person.
Who gets it
One of the most common skin diseases and the leading occupational skin disease. Hand dermatitis is frequent in health workers, hairdressers, cleaners, cooks, construction and agricultural workers, including farm workers in Colombia exposed to cement, pesticides and plants.
Causes
- Irritants: frequent handwashing and wet work, soaps and detergents, solvents, alkalis and acids, friction
- Allergens: nickel (jewellery, belt buckles, watches), fragrances and preservatives in cosmetics
- Rubber accelerators in gloves, hair dye (para-phenylenediamine), topical antibiotics such as neomycin
- Plants (e.g. urushiol in poison ivy-type plants) and occupational chemicals (chromate in cement, epoxy resins)
Risk factors
- Occupations with wet work or chemical exposure, including nursing and other health care
- History of atopic dermatitis (damaged barrier)
- Piercings and contact with metal jewellery
- Repeated use of topical products, cosmetics and hair dyes
- Frequent use of latex gloves (also risk of immediate latex allergy)
Pathophysiology
In irritant dermatitis, the substance directly damages keratinocytes and the lipid barrier, releasing inflammatory cytokines; anyone exposed enough will react. In allergic dermatitis, a small molecule (hapten) binds skin proteins and is presented by Langerhans cells to T cells (sensitisation phase). On re-exposure, memory T cells cause eczema 24–72 hours later (elicitation). Immediate latex allergy is different: an IgE-mediated type I reaction that can cause hives and anaphylaxis.
Classification
- Irritant contact dermatitis (about 80%)
- Allergic contact dermatitis (type IV hypersensitivity)
- Photoallergic and phototoxic contact dermatitis
- Contact urticaria, including immediate (type I) latex allergy
Symptoms and signs
- Itch (more in allergic) or burning and stinging (more in irritant)
- Red, scaly or vesicular patches with sharp borders matching the area of contact
- Linear streaks of vesicles after brushing against plants
- Dry, cracked, thickened skin on the hands in chronic irritant dermatitis
- Rash under a ring, watch, earrings, belt buckle or glove, or on the eyelids from products transferred by the hands
Diagnosis
- Clinical
- Pattern and shape of the rash, its site and a detailed exposure history (work, hobbies, cosmetics, jewellery, gloves, topical medicines); improvement away from work supports an occupational cause.
- Tests
- Patch testing is the standard test for allergic contact dermatitis, read at about 48 and 96 hours. There is no test for irritant dermatitis. For suspected immediate latex allergy: specific IgE to latex in blood or a skin prick test by specialists.
- Imaging
- Not needed.
Differential diagnosis
- Atopic dermatitis
- Tinea (dermatophytosis) of hands or feet
- Psoriasis and dyshidrotic eczema
- Scabies
- Cellulitis (for acute facial or limb swelling)
Goal of treatment
Identify and avoid the irritant or allergen, repair the skin barrier and control inflammation, and protect people with latex allergy from any latex exposure.
Treatment
- Conservative
- Avoiding the cause is the key measure: substitute products, nickel-free jewellery, appropriate protective gloves (nitrile or vinyl), and frequent use of fragrance-free emollients and barrier creams.
- Medical
- Topical corticosteroids of potency suited to the site (low on face and eyelids, higher on hands); topical calcineurin inhibitors for the face and eyelids.
- Medical
- Short course of systemic corticosteroids for extensive or severe allergic dermatitis such as widespread plant dermatitis; oral antihistamines mainly for sleep.
- Acute
- Known latex allergy: a latex-free environment (gloves, catheters, tourniquets, BP cuffs, syringes), an allergy band and record, and readiness to treat anaphylaxis; ask about reactions to banana, avocado, kiwi or chestnut (latex-fruit syndrome).
Complications
- Secondary bacterial infection (impetiginisation)
- Chronic hand eczema and loss of work
- Spread of the reaction beyond the contact area (autoeczematisation)
- Anaphylaxis in immediate latex allergy
Prognosis
Clears within weeks when the cause is avoided. Allergic sensitisation usually lasts for life, so avoidance must continue; chronic occupational hand dermatitis can persist despite treatment.
Prevention
- Protective gloves and moisturisers in wet or chemical work
- Using powder-free, non-latex gloves in health care
- Reading product labels and avoiding known allergens
Test yourself
Think of the answer, then tap the question to see it.
What type of hypersensitivity is allergic contact dermatitis?
Type IV, delayed, T-cell-mediated hypersensitivity, appearing 24–72 hours after re-exposure.
Which is the most common allergen in allergic contact dermatitis?
Nickel, from jewellery, watches and belt buckles.
What test confirms allergic contact dermatitis?
Patch testing, read at about 48 and 96 hours.
Which foods suggest cross-reactivity in a patient with latex allergy?
Banana, avocado, kiwi and chestnut (latex-fruit syndrome).
What is the first nursing priority for a patient with a known latex allergy?
A latex-free environment and equipment, a visible allergy alert and readiness to treat anaphylaxis.
Related conditions
- Anaphylaxis
- Urticaria and angioedema
- Scabies
- Dermatophytosis (tinea) and onychomycosis
- Impetigo
- Allergic rhinitis
- Asthma
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Contact dermatitis (MedlinePlus (U.S. National Library of Medicine), 2024); Latex Allergy (MedlinePlus (U.S. National Library of Medicine), 2024).
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