Enzymes, Detergents and Skin: Facts and Fantasies

D.A. Basketter; J.S.C. English; S.H. Wakelin; I.R. White

Disclosures

The British Journal of Dermatology. 2008;158(6):1177-1181. 

In This Article

Irritation

It has long been recognized that a combination of wet work and detergent/surfactant exposure can lead in many individuals to skin irritation, most often expressed as hand eczema.[10,11,12] In this section, the evidence that normal consumer use of enzyme-based laundry detergents can lead to skin irritation is considered. Special attention is paid to whether there may be susceptible subpopulations who might be predisposed to the development of this effect.

As with all toxicological effects, clinical skin irritation arises from a combination of the hazardous properties of materials and exposure, in this case, skin exposure. The surfactants in laundry products are known to have the intrinsic ability to cause skin irritation. This can occur as a consequence of repeated exposures to the diluted solutions used during normal laundry procedure and can be simulated in suitable exposure studies.[13,14] It is the authors' view that nowadays consumers do not normally experience this problem as they are aware of the risk and tend to avoid repeated/prolonged contact together with rinsing hands after any exposure. Typically, manufacturers provide guidance in this respect on their packaging.

In an early and comprehensive study, 739 subjects took part in several double-blind cross-over tests involving a range of main wash and presoak detergent formulations, with and without proteolytic enzymes.[14] In their patch tests, detergent formulations containing enzymes or enzyme concentrates applied under occlusion were more irritating to the skin than nonenzymatic controls. However, this type of exposure is grossly exaggerated compared with normal consumer contact and has been shown to lead to irrelevant results.[15] With the tests employing exaggerated use conditions, there was no significant increase in skin irritation in any of the hand or arm immersion assays that could be attributed to the presence of enzyme.[15] To confirm that the increased irritancy of the enzyme-containing formulations seen in patch tests would not result in any adverse effects during normal use, further tests were conducted. Products were used normally in a total of 5943 subjects and the hands examined by a dermatologist. No differences were observed between the enzyme and control treatments. In the second (involving 360 infants), babies' nappies were washed in the test and experimental products and the nappies worn. There was no difference in the incidence or severity of nappy rash between groups of infants wearing nappies laundered in the products with or without enzymes.[14]

The direct effects of wash solutions under reasonably foreseeable use conditions were evaluated by Bolam and colleagues.[16] Consumers were asked to use a laundry detergent containing a proteolytic enzyme or an enzyme-free product for 2-week periods for dishwashing and general household cleaning as well as for hand-washing fabrics, in order to simulate extended consumer use, including uses not intended by the product manufacturer. The results of this work showed that the addition of proteolytic enzymes did not enhance irritancy. As other classes of enzyme are of lesser intrinsic irritant hazard potential, then clearly they would also not induce skin irritation reactions in practice.

In a rigorous series of investigations in Germany reported in a pair of publications, the effects of enzyme-containing detergents on the skin were examined.[17,18] Undertaking studies not only of normal but also of irritated, acid or alkali damaged or tape-stripped skin, several days of skin contact with enzyme dilutions were without effect (in total, 912 tests were completed). As mentioned in the introduction to this review, the authors concluded that any effects caused by laundry detergents could not be due to the (proteolytic) enzyme content. In a second phase of the work, enzyme-containing and enzyme-free formulations were employed in a study design which intended to produce visible skin irritation; the formulation with enzyme behaved in the same manner as the enzyme-free formulation, confirming that the enzyme at the product use concentration was not making a detectable contribution to the skin irritation potential for the formulation.[18]

There are also several published reports on the lack of irritant effects of enzyme residues on fabrics.[19,20] These studies employed 2-day patch tests of fabrics containing detergent residues and a variety of exaggerated exposure tests. In all the studies, no evidence that residues in the fabrics caused irritancy was obtained. Similar results were obtained by Rodriguez and colleagues who used a variety of European detergents under European washing conditions.[21]

More recently than the above studies, but still completed a decade ago, was the excellent work undertaken by a Danish group.[22] These workers completed a placebo-controlled blinded study of some months' duration, concluding that 'it is unlikely that consumers with ''normal skin'' will experience any skin discomfort when enzyme-enriched detergents are used'. This conclusion was reached on the basis of a study using 25 patients with atopic dermatitis, individuals commonly considered to be much more likely to experience adverse skin effects,[23] but who in fact showed no greater reaction to the enzyme-containing products than to those without enzymes.

Ultimately, the balance of all the evidence, much of which is reviewed above, is that enzymes in laundry detergents are not a cause of skin irritation in practice.

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