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INTRODUCTION

Contact dermatitis refers to a group of dermatoses presenting as an inflammatory eczematous reaction as a consequence of direct contact with an exogenous agent. Based on the pathophysiology, it can be categorized into irritant contact dermatitis, allergic contact dermatitis, photocontact dermatitis, contact urticaria, and less common non-eczematous clinical manifestations of contact dermatitis.

IRRITANT CONTACT DERMATITIS

As the name suggests, irritant contact dermatitis refers to skin inflammation that occurs as a result of direct skin contact with a noxious agent (Figures 3–1, 3–2, 3–3, 3–4, 3–5, 3–6, 3–7, 3–8, 3–9, 3–10, 3–11).

Figure 3-1

Irritant contact dermatitis to plaster

This patient developed irritant contact dermatitis to the plaster that she applied over the arteriovenous fistula site on her left forearm post dialysis. There is a well-demarcated, scaly, erythematous plaque where the plaster has been applied. The patch test was negative.

Figure 3-2

Irritant contact dermatitis to epoxy resin and adhesives

Scaly eczematous patches are seen over the palmar aspects of the patient’s distal phalanges and thenar eminences. This patient works as a technical specialist with frequent contact with epoxy resin and adhesives. The patch test was negative.

Figure 3-3

Irritant contact dermatitis to epoxy resin and adhesives

Scaly, hyperpigmented, lichenified plaques are also seen over the proximal nail folds of the same patient. The patch test was negative.

Figure 3-4

Cumulative insult irritant contact dermatitis to dishwashing liquid.

This often occurs on susceptible skin of patients with an atopic diathesis after repeated exposure to mild irritants such as detergents and water. Scaling and lichenification of the hand are seen in this patient, which indicate chronic eczema due to repeated exposure to chemical irritation. She has a history of allergic rhinitis and works as a cleaner in the catering industry. Water and detergents are some of the most common causes of irritant contact dermatitis in Singapore.

Figure 3-5

Acute irritant contact dermatitis to medicated oil

An erythematous patch with vesicles is present over the patient’s left upper chest. This patient has underlying endogenous eczema and has been applying medicated oil to his left anterior chest to ease his itch. Topical medicaments such as traditional medicated oils and antiseptics are among the most common causes of irritant contact dermatitis in our local population, and may aggravate pre-existing dermatosis.

Figure 3-6

Irritant contact dermatitis to skin whitening cream

This patient was troubled by the solar lentigines on her cheeks and attempted to lighten the lentigines by applying a ...

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