The potential for cosmetic formulations to induce skin irritation is an important consideration for cosmetics producers. Irritation potential may be predicted by in vitro systems, provided they are sufficiently complex to mimic the skin barrier in vivo.
The objective of this work was to evaluate the dermal irritation potential of different cosmetic formulations using the human epidermis model, EpiDerm. Our study showed that in vitro tests, as an alternative to animal testing, allow for preliminary assessment of a cosmetic formulation’s irritation potential. However, further studies are required to evaluate the usefulness of in vitro epidermis models to predict in vivo skin irritation.
Skin irritation, accompanied by typical inflammation symptoms like erythema, edema, dryness, desquamation and itching, is the most common adverse effect in humans. The source of the irritant is most often a chemical. The main pathological mechanisms of irritancy include skin barrier disruption, induction of a cytokine cascade and involvement of the oxidative stress network; all of which result in a visible or subclinical inflammatory reaction.1–3 Interleukin-1??(IL-1?) is believed to be the main switch in the initiation of cutaneous inflammation. It has been hypothesised that IL-1??is derived from the damaged keratinocytes during the interaction between the irritant and epidermal barrier.1–4 Until recently, identifying irritants has relied entirely on animal testing, such as the Draize rabbit skin test; a classic example introduced into safety tests for drugs and chemicals 60 years ago, which involves applying the product to a rabbit’s skin.5 In accordance with EU law, a ban on animal testing of cosmetics has been in force since 2004, whereas since 2009 (for repeated dose toxicity test, reproductive toxicity and toxicokinetics until 2013) all animal testing for ingredients used in cosmetics production has been stopped.6 Therefore, safety tests with the use of in vitro method are a field of toxicology which, currently, is undergoing intense development. On the other hand, the Registration, Evaluation and Authorization of Chemicals (REACH) legislation has stimulated the development of alternative tests for the assessment of potential toxicological effects of substances.7 The development of molecular investigative techniques led to the introduction of different in vitro models for the assessment of irritant properties. Human epidermal equivalents are one of the most extensively studied models to determine the irritant potential of a chemical in vitro. Until now, the EpiSKIN, EpiDerm and SkinEthic models have been validated by ECVAM (European Centre for the Validation of Alternative Methods). They consist of fully differentiated reconstructed human epidermis and are able to mimic the human epidermis. The presence of the functional stratum corneum in epidermal equivalents means that, in a similar way to human skin, the cultures have a barrier function and therefore test substances (water soluble or insoluble) can be applied topically in a similar manner to patch testing human volunteers.3,8 The aim of this study was to evaluate the dermal irritation potential of cosmetics using in vitro tests. For that purpose, five cosmetic formulations were tested in vitro using the commercially available epidermis equivalent, EpiDerm (now referred to as “the skin model”).
Experimental
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