Chapter 8: Dermatitis

INTRODUCTION TO CHAPTER

Dermatitis (eczema) refers to a heterogeneous group of disorders that share similarities in clinical appearance and histopathologic findings, but may have very different etiologies. Eczema originates from a Greek word meaning "to boil." Acute dermatitis often appears vesicular (like water boiling on the skin), whereas chronic dermatitis may be red, scaly, and lichenified. Pruritus is a common symptom of all types of dermatitis.

CONTACT DERMATITIS

The 2 major types of contact dermatitis are irritant contact dermatitis and allergic contact dermatitis. These reactions are not mutually exclusive, and may occur simultaneously in a particular patient. For example, contact allergy to a glove chemical may complicate irritant hand dermatitis due to irritating soaps used for hand washing. Furthermore, one substance may act as both an irritant and an allergen; a patient may have an allergic reaction to a preservative in a liquid soap as well as having an irritant reaction to a detergent in a soap. Common allergens include urushiol (eg, poison ivy), nickel, fragrances, preservatives, topical antibiotics (eg, neomycin, bacitracin), and paraphenylenediamine (eg, black hair dye). Common irritants include water, soap, industrial cleansers, and frictional forces.

IRRITANT CONTACT DERMATITIS

Introduction

Irritant contact dermatitis is the most common form of contact dermatitis. It is estimated that irritant contact dermatitis represents approximately 80% of occupational contact dermatitis. Occupations at high risk include those involving repeated exposure to water and/or soap (wet work) such as health care workers, janitorial services, and food industry employees or those involving exposure to solvents such as machinists.¹

Pathophysiology

Irritant contact dermatitis is a nonimmunologic response to chemicals or physical agents such as friction that disrupt the normal epidermal barrier. Strong irritants include acids and alkalis, whereas weak irritants include soaps and cleansers. Damaged skin lacks the proper oils and moisture, thus allowing irritants to penetrate more deeply and cause further damage by triggering inflammation. Any condition that impairs skin barrier function, such as atopic dermatitis or asteatotic dermatitis/dry skin, is a risk factor for developing irritant contact dermatitis.

Clinical Presentation

History

Irritant contact dermatitis typically develops weeks after exposure to weak irritants such as hand soap or immediately after exposure to strong irritants such as bleach. It may affect any individual, given sufficient exposure to irritants, but those with a history of atopic dermatitis are at higher risk because of disruption of the normal epidermal barrier. Pruritus, pain, and burning are common symptoms.

Physical Examination

Irritant contact dermatitis is often well demarcated with a glazed appearance, but there may also be erythema, swelling, blistering, and scaling. Initially, irritant reactions are usually confined to the site of contact with the irritant. The most common locations are hands, ...