Mechanical skin damage

Skin irritation caused by skin stripping at the removal of PSA When the adhesive strength between the adhesive and the outmost stratum corneum cell is stronger than the intercellular binding force between stratum corneum cells, the outmost stratum corneum cells will be transferred from the skin to the adhesive when PSA is peeled from skin. This mechanical skin damage also causes pain and skin irritation. 

Soldiers, by the nature of their profession, are at increased risk of mechanical skin damage. Friction blisters of the extremities are common (Hoeffler 1975) Knapik et al. (1992) reported that 69% of 335 soldiers participating in a maximal-effort road march developed foot blisters. Chronic or intermittent low-intensity irritation induces epidermal thickening, and strong acids (sulfuric, hydrochloric) and alkalis may cause chemical cauterization on contact with the skin (Shaposhnikov 1973 Naidenov 1980). 

Three percent of o-limonene was found to cause skin damage. However, instead of roughening, the damage caused smoothing as shown by a decrease of fractal dimension and was suggested to be a result of hydration and/or edema formation in the shallow part of the skin.f Hence fractal analysis can be used to elucidate the damage mechanism and provides quantitative measurement of skin damage. ... 

Observable toxic responses in the skin (irritation, allergic reaction) can be directly caused by the presence of surfactant molecules in the dermis, by inflammatory mediators (cytokines) liberated by keratinocytes, or by other substances penetrating the epidermis after the skin barrier function has been impaired by surfactants. The damage of hair fibers is closely related to the impairment of the cuticle layer, which can cause modifications in the mechanical and optical properties of the hair. Substantial differences exist between the mechanisms of skin damage and hair damage, but for the purposes of our discussion, only the common initial event of surfactant-keratin interaction will be considered. 

The severity of skin damage by chemical agents depends on (1) strength or concentration of the agent, (2) quantity of the agent, (3) duration of skin contact, (4) extent of penetration into tissues, and (5) mechanism of action. 

Much work has been done to understand more about the mechanisms behind the development of chronic irritant dermatitis. This started with the identification of this pattern of irritation in the 1970s by Malten. He stndied the symptoms of occupational workers exposed to a variety of chemicals that led to a nnmber of similar symptoms that seemed to indicate allergic contact dermatitis, but yet were not sensitized [50, 51]. Malten also was the first to nse instmmental measurements for water loss and skin impedance to characterize skin damaged by cnmnlative irritation [52], This understanding and nse of instm-mentation to numerate physiological changes in those affected by cumulative irritation led the way in the development of methods that are now widely used by clinicians to understand the mechanism behind cumulative irritation. 

Tables 4.7, 4.8, 4.9, and 4.10 summarize 14 in vivo human skin studies, which compare penetration variance through damaged versus intact skin. Categories of skin damage include mechanical, UVB, chemical, and clinical disease. Tables 4.11,4.12, and 4.13 are separate tables for those studies in which microdialysis was the mode of measurement. Because penetration...

Local repair of delamination originally caused by non-durable surface treatment is only temporarily successful at best. The surface treatment on the unrepaired portion of the assembly remains susceptible to attack and the area of delamination will likely continue to grow once the assembly is put back into service and exposed to moist conditions. Replacement or complete remanufacture of the component is the only way to permanently address this type of damage. However, time-limited repairs using bonded or mechanical methods can be used to extend the life of the component until a major overhaul is scheduled. In some cases such as widespread disbond of fuselage doublers, mechanical repairs (rivets and fastened doublers) and continued inspection are used to extend the life of the skin indefinitely because of the high cost of replacement. 

Ultraviolet wavelengths of 290-310 nm from the UV-B band of radiation constitute the principal tissue-damaging rays of the sun, which are not fully atmospherically filtered. An hour s exposure to the summer sun and its damaging rays can produce a painful burn with a characteristic erythema. The skin has natural mechanisms to prevent or minimize such sun-induced trauma, but it takes time to set these into place. Upon... 

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