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A Review of Anti-Irritants, Part I: Barrier Cream Efficacy on Contact Dermatitis*
By: Howard I. Maibach, MD, University of California School of Medicine; and Hongbo Zhai, MD, University of California
Posted: March 2, 2011, from the March 2011 issue of Cosmetics & Toiletries.
Irritant contact dermatitis (ICD) is a common form of irritation that can occur when human skin is exposed to potential irritants such as surfactants, cutting oils, etc.1, 2 Minimizing exposure to such irritants is recommended but often not practical since exposure is unavoidable in some occupations including farming, firefighting, medicine, etc. To counteract or suppress irritation responses in the skin, anti-irritant agents are employed. These ingredients, whether naturally occurring or man-made, used alone or in formulations, possess the capacity to reduce irritation caused by acute and chronic exposure to irritants.3
To fully prevent or reduce the risk of developing ICD, anti-irritant agents such as barrier creams (BCs) and moisturizers are widely utilized.4–9 Though BCs and moisturizers are not identical, probably due to their ambiguous definitions, the terms BC and moisturizer are often used interchangeably in the literature and the marketplace. The target of BCs is to prevent external noxious substances from penetrating skin, usually in an occupational setting,5, 7–9 whereas moisturizers are frequently used for dry skin conditions as well as to maintain healthy skin.4, 6, 9–11 However, moisturizers and BCs share characteristics, thus it can be difficult to distinguish between the two. Therefore it is suggested that the standard term skin protectant be used when referring to anti-irritants;12 several terms and definitions commonly used in reference to skin protection are summarized in Table 1. Although numerous ingredients have been formulated into finished skin protection products, the US Food and Drug Administration (FDA) has only endorsed 13 ingredients for over-the-counter (OTC) products (see Table 2).
Based on an extensive literature review, this column describes studies and data related to the proposed efficacy of anti-irritant agents for reducing ICD in human skin. To compile this review, a literature search in PubMed, EMBASE and Scopus was conducted, and only research discussing either the prevention or treatment of irritation in human skin was considered. Studies and data conducted on non-human skin were excluded, and emphasis was placed on the studies that included quantitative and qualitative results as well as those that followed evidence-based dermatological guidelines.
For the purpose of this review, anti-irritant is defined as a moiety that either inhibits (prevents) or treats ICD. Specific focus was placed on the clinical markers of irritation—i.e., edema, erythema, vesiculation and diminished barrier function—as these are more readily and objectively assessed with visual scoring criteria and bioengineering measurements.
As noted, ICD is the result of an unspecific amount of damage to the skin from contact with irritating chemical substances.1, 4 Exposure to irritants such as solvents, detergents and even water13 can lead to stratum corneum damage, resulting in skin barrier impairment.4 While the exact mechanisms of irritant reaction are not completely understood, it seems likely that there is an immunologiclike component to the irritant response.1 The clinical appearance of ICD varies depending on multiple internal and external factors.1, 3 Airborne ICD may develop in uncovered skin areas, mostly in the face and neck, after exposure to volatile irritants or vapor. Prophylactic measures can be taken to reduce the risk of ICD—and oftentimes, BCs and moisturizers as well as anti-irritant agents may play a key role in this strategy.