15th July 2026

Dermatitis

Allergic contact dermatitis

Clinical features

Allergic contact dermatitis is associated with Type IV hypersensitivity reaction. It requires previous exposure to the substance (sensitisation). Rash usually takes around 48-72 hours after the exposure to appear. Usually confined to contacted area, but can sometimes extend outside the contacted area or may be generalised. Reaction usually produces erythema, oedema and blisters. Diagnosis usually can be made with detailed and careful history taking on exposure to common allergens.

Common sources of allergic contact dermatitis include

Nickel, Chromate
Hair dyes(paraphenylenediamine), tights, shoes
Creams, ointments, cosmetics

Investigations

Patch testing

Management

Avoidance of allergens
Emollient creams
Topical steroids
Oral antibiotics if secondary infection
Topical calcineurin inhibitor

Irritant contact dermatitis

Clinical features

Irritant contact dermatitis is a non-allergic reaction which commonly affects the hands. It is due to repetitive exposure to irritants on the skin. Erythema is normally confined to the area of exposure to the irritant. In acute phase, it can present with erythema, swelling, papules and blisters. It usually occurs soon after the exposure, and severity is dependent on a few factors such as length of exposure, concentration and quantity of irritants. Frequent hand scrubbing, exposure to temperature extremes, and humidity can cause irritant contact dermatitis. It can happen because of the cumulative impact of multiple irritants.

Common sources of allergic contact dermatitis include

Detergent
Cement
Organic solvent
Friction
Hand sanitisers

Investigations

Diagnosis is mainly from history taking and clinical examination.
Patch testing may be used to distinguish between allergic and contact dermatitis.

Management

Avoid all potential irritants
Emollient
Barrier creams +/- topical steroids.

Atopic Dermatitis

Clinical features

Atopic dermatitis is also known as atopic eczema. It is the most common inflammatory dermatitis. It tends to affect people with positive family history or personal history of atopy. Usually starts from infancy and may settle in late childhood or adolescence. All ages can be affected. Risk factors for developing atopic dermatitis can be broken down into genetic and environmental risk factors. Genetic: positive family history, filaggrin gene defects (FLG), which cause a skin barrier defect, and the immune system (Th2-associated cytokines contribute to loss of skin barrier function). Environmental factors include dry skin associated with low humidity, frequent hand washing, winter weather, and irritants such as detergents.

It commonly affects the flexural aspect of the skin; however, it can affect all parts of the skin depending on age. In darker skin types, it may also affect the extensor surfaces more commonly than in lighter skin types. In chronic cases, skin may become thickened (lichenified) and less erythematous compared to the acute phase.

Investigations

Normally, a clinical diagnosis
Patch testing may be utilised in treatment-resistant cases.

Management

Avoidance of irritants or exacerbating factors
Topical therapy such as regular emollients, topical steroids, topical antibiotics (if only secondary infection), and topical calcineurin inhibitors
Phototherapy: UVB or PUVA
Systemic treatment: Prednisolone (severe flare), ciclosporin, azathioprine, antihistamines
Janus Kinase Inhibitor: Abrocitinib, bariticinib
Biologics: Dupilumab, Tralokinumab

Steroid Potencies

Mild	Moderate	Potent	Very Potent
Hydrocortisone 0.5%-2.5%	Betamethasone valerate 0.025% ClobetaSONE butyrate 0.05% (Eumovate)	Betametasone valerate 0.1% (Betnovate)	ClobetaSOL propionate 0.05% (Dermovate)

Complications

Secondary infection:
- Bacterial – Staphylococcus and streptococcal infection
- Viral – Eczema herpeticum, Eczema coxsackium, Molluscum contagiosum
- Fungal- Dermatophyte (Trichophyton rubrum / Epidermophyton skin infection)

Child with facial eczema herpeticum

Child with facial eczema herpeticum.

Image Source: Wikimedia Commons (2020), ECG AVNRT, Licenced under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Eczema_herpitcum.jpg (Accessed: 24 May 2026).

Clinical features

Eczema Herpeticum is commonly seen as a complication of atopic dermatitis. It is characterised by monomorphic painful and itchy blisters with punched out lesions, and new blisters have a central dimple (umbilication). It is caused by Herpes Simplex Virus(HSV)Type 1 or 2. It can also happen in non-eczematous conditions such as thermal burns and psoriasis. The patient can be very unwell and present with fever and swollen lymph nodes. Eye involvement will require urgent ophthalmology attention.

Investigations

Viral swabs
Bacterial swabs
Rule out secondary infection.

Management

Oral antiviral, e.g., Aciclovir 400mg, five times a day
Oral antibiotics if secondary bacterial infection
Topical steroids generally NOT recommended unless there is active underlying atopic dermatitis that requires treatment

Dyshidrotic eczema (Pompholyx)

Clinical features

Pompholyx is characterised by vesicles and can be as large as bullae, usually deep-seated on the palms and soles. It is often associated with intense itchiness and a burning sensation. Once the blisters healed, the skin can become red, dry and cracked. However, most of the time, the vesicles will gradually subside or resolve spontaneously. Up to 50% of patients will have a family or personal history of atopic dermatitis. Females are more commonly affected than males. Cause of the rash is unknown and thought to be aggravated by hot and humid weather, emotional stressors, exposure to irritants or allergens.

Investigations

Usually diagnosed clinically
Skin biopsy can be performed if diagnosis is uncertain
Patch testing can be used if a component of allergic dermatitis is suspected

Management

General measures include wet dressings to dry up blisters, such as diluted potassium permanganate, emollient, antiperspirant applied to palms and soles at night, and wear gloves if working with irritants or allergens
Topical steroids- Greater potency steroid is normally used, given thick skin on palms and soles
Antibiotics if infection present

Seborrhoeic dermatitis

Clinical features

Seborrheic dermatitis is a self-limiting, chronic and relapsing skin condition. It has a biphasic model, which affects infants and peaks in adults. It mainly affects areas with rich sebaceous glands, such as the face (eyebrow, eyelid, cheeks), scalp and trunk. It can affect the eyelid, causing blepharitis or scaly patches or scales on the scalp. The lesion has a defined margin, dull red or yellowish, covered with greasy scale. In adults, Malassezia furfur growth plays a role in the pathogenesis of seborrhoeic dermatitis. There are a few conditions known to be associated with severe seborrhoeic, such as HIV and Parkinson’s disease.

Seborrhoeic dermatitis is usually associated with flares during the winter months and improves during the summer. Itchiness is not a common feature. Salmon pink scaly rash can be seen on the facial folds. On the scalp, the presentation ranges from mild dandruff to scaling of the scalp.

Investigations

Usually, a clinical diagnosis
Consider investigations for associated conditions, such as HIV in refractory cases

Management

Scalp: first line: Shampoo with zinc pyrithionine, tar shampoos, ketoconazole shampoos
Other parts of the body: Topical antifungal such as ketoconazole 2% cream for facial involvement, Ketoconazole 2% bodywash can be used on trunk involvement
Mild topical corticosteroid can be considered if there is active inflammation

Discoid Dermatitis (Nummular Eczema)

Clinical features

Discoid dermatitis is characterised as single or multiple, itchy, well-defined, coin-shaped, erythematous plaques with +/- vesiculation. It usually involves the lower legs, the forearm and the dorsum of the hand. It commonly affects young women and middle-aged adults. The cause of this is unknown; it is associated with contact allergy manifestation of atopy or localised injury.