Excerpt from Contact Dermatitis, Irritant

Synonyms, Key Words, and Related Terms: nonallergic contact dermatitis, ICD

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Background: Irritant contact dermatitis (ICD) is inflammation of the skin typically manifested by erythema, mild edema, and scaling. ICD is a nonspecific response of the skin to direct chemical damage that releases mediators of inflammation predominately from epidermal cells. A corrosive agent causes the immediate death of epidermal cells as manifested by chemical burns and cutaneous ulcers.

ICD remains understudied compared to allergic contact dermatitis. Most articles on contact dermatitis concern allergic contact dermatitis. This largely reflects the fact that with patch testing, a specific hypersensitivity and a probable cause of dermatitis can be identified in most cases of allergic contact dermatitis. No diagnostic test exists for ICD. The diagnosis rests on the exclusion of other cutaneous diseases (especially allergic contact dermatitis) and on the clinical appearance of dermatitis at a site sufficiently exposed to a known cutaneous irritant.

In the consumer world, the term hypoallergenic is used widely, although no Food and Drug Administration–approved definition of hypoallergenic exists. A necessity exists for hypoirritating cleansers, cosmetics, moisturizers, and protectants; however, no standard method exists to identify products that are of great use to individuals with susceptible skin (eg, atopic dermatitis, facial skin of individuals with rosacea).

The hands are the most important sites of ICD. Most occupational skin disorders are ICD resulting from repeated workplace exposure of the hands to soaps, cleansers, and solvents.

Pathophysiology: ICD is the clinical result of sufficient inflammation arising from the release of proinflammatory cytokines from skin cells (principally keratinocytes), usually in response to chemical stimuli. Different clinical forms may arise. The 3 main pathophysiological changes are skin barrier disruption, epidermal cellular changes, and cytokine release.

A wide range of chemicals with sufficient concentration or duration of exposures are capable of acting as cutaneous irritants. Common cutaneous irritants include detergent and water. Most cases of housewife's eczema are ICD resulting from repeated skin exposure to low-grade cutaneous irritants, particularly soaps, water, and detergents.

Cumulative ICD from repeated mild skin irritation from soap and water is common. For example, hand-washing frequency of more than 35 times per shift was associated strongly with occupational hand dermatitis in intensive care unit workers (odds ratio=4.13).

Solvents are another major cause of cutaneous irritation because they remove essential fats and oils from the skin, which increases transepidermal water loss and renders the skin susceptible to the increased direct toxic effects of other previously well-tolerated cutaneous exposures.

Microtrauma also may produce skin irritation. A common example is fiberglass, which may produce pruritus with minimal visible inflammation in susceptible individuals. Many plant leaves and stems bear small spicules and barbs that produce direct skin trauma.

Physical irritants (eg, friction, abrasive grains, occlusion) and detergents such as sodium lauryl sulfate (SLS) in combination produce more ICD in combination than singly.

Skin irritation predisposes the skin to develop sensitization to topical agents. An exacerbation of ICD may reflect development of allergic contact dermatitis to topical creams, medications, or rubber gloves.

The pathogenesis of ICD involves resident epidermal cells, dermal fibroblasts, endothelial cells, and various leukocytes interacting with each other under the control of a network of cytokines and lipid mediators. Keratinocytes play an important role in the initiation and perpetuation of skin inflammatory reactions through the release of and responses to cytokines. Resting keratinocytes produce some cytokines constitutively.

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