Eschar formation

Severe erythema (beet redness) to slight eschar formation (injuries in depth) 4... 

A Subtotal Irritation Value for erythema or eschar formation is determined for each rabbit by adding the values observed at 25, 48, and 72 h postapplication. 

D. Analysis of data The data from the irradiated and nonirradiated sites are evaluated separately. The scores from erythema and eschar formation, and edema at 24, 48, and 72 hr, are added for each animal (six values). The six values are then divided by 3, yielding six individual scores. The mean of the six individual animal irritation scores represents the mean primary irritation score (maximum score = 8, as in the primary dermal irritation study). This method was developed after a human model had been developed. 

In another 1964 experiment, 10 subjects had H at 2 g/10 cm on three separate swatches of protective cloth taped to their arms. The protocol notes that the cloth was protective in nine subjects. One subject was hospitalized when the exposed area vesicated with later eschar formation. 

Skin and Eye Irritation The solvent should not be a skin or eye irritant. A product is considered to be a skin irritant if it has a mean score of 2 or more for either erythema and eschar formation or edema formation, based on the OECD dermal scoring system (OECD, TG 404). A product is classified as an eye irritant if it causes significant ocular lesions, in any type of ocular tissue (i.e., cornea, iris, or conjuncti-vae) within 72 hours after exposure and which persist for at least 24 hours. 

Single-dose dermal LD50 values in New Zealand rabbits exposed to chromium(VI) as sodium chromate, sodium dichromate, potassium dichromate, and ammonium dichromate were determined by Gad et al. (1986). LD50 values ranged from 361 to 553 mg chromium(VI)/kg for females and from 336 to 763 mg chromium(VI)/kg for males. Signs of toxicity included dermal necrosis, eschar formation, dermal edema and erythema, and diarrhea and hypoactivity. The dermal LD50 value for chromium trioxide was 30 mg chromium(VI)/kg for combined sexes (American Chrome and Chemical 1989). The LD50 values are recorded in Table 2-3. 

Similar dermal effects have been observed in animals. Dermal application of chromium(VI) compounds to the clipped, nonabraded skin of rabbits at 42-55 mg/kg resulted in skin inflammation, edema, and necrosis. Skin corrosion and eschar formation occurred at lethal doses (see Section 2.2.3.1) (Gad et al. 1986). Application of 0.01 or 0.05 mL of 0.34 molar solution of potassium dichromate (0.35 mg chromium(VI) or 1.9 mg chromium(VI)/kg) to the abraded skin of guinea pigs resulted in skin ulcers (Samitz 1970 Samitz and Epstein 1962). Similar application of 0.01 mL of a 1 molar solution of chromium sulfate (1 mg chromium(ni)/kg) however, did not cause skin ulcers in guinea pigs (Samitz and Epstein 1962). 

Dermal effects observed in animals after direct application of potassium dichromate to their skin include inflammation, necrosis, corrosion, eschar formation, and edema in rabbits (Gad et al. 1986) and skin ulcers in guinea pigs (Samitz 1970 Samitz and Epstein 1962). 

The Draize test provides tremendous value in warning consumers, workers and manufacturers of potential dangers associated with specific chemicals so that appropriate precautions can be taken. Although vesiculation, ulceration, and severe eschar formations are not included in the Draize Scoring Scales, all Draize-type tests are used to evaluate corrosion as well as irritation. 

The mean values of the six rabbits for erythema and eschar formation at 24 and 72 h for both intact and abraded skin (four values) are added. The mean values of the six rabbits for edema at 24 and 72 h (four values) are also added. The total of eight values is divided by 4 to give the primary irritation index. Values of 5 or greater are considered indicative of a positive irritant. ... 

Propargite exhibits low acute toxicity via oral and dermal exposures. The oral LD50 value in rats is about l gkg. With dermal exposure, the LD50 values are 250 mg kg (male) and 680 mg kg (female) in rats and > 3 g kg in rabbits. Propargite is, however, a strong eye and skin irritant that causes erythema, edema, and eschar formation in rabbits. 

Skin Reaction Erythema and eschar formation Value ... 

Table I shows that a 3x3.5 cm dorsal skin wound on a Wistar rat can ooze out 2.2 ml of serous fluid in about 3 days. This fluid volume is reduced to 1.2 ml, if the wound is exposed for 3 hr before treatment. Beyond the 3 hr exposure, there may be further reduction in oozing, but the chance of eschar formation will also increase. Various compositions of the AgN03 medicated dextran hydrogel paste have been evaluated. The one with a good spreadability and fluid absorption has been used in the present study. Measurements by a simple hygrometric method showed that the medicated paste on the wound reduced evaporative loss by almost 50% as compared to an open wound which had a rate of 93 mg H20/cm /hr (7.). On subsequent days, the relatively steady value of 12.5 mg H20/cm /hr was about 2x higher than the evaporative loss of the paste spread over a plastic sheet used as a control. The higher evaporative rate of the paste on the wound site might be due to the transmission of excess moisture from the wound surface. The oozing serous fluid had apparently been first absorbed into the paste, because no exudate accumulation was ever observed under the paste coating. The humectant in the paste which retained moisture obviously must have kept the wound surface sufficiently moist to prevent eschar formation.

The skin is damaged by direct binding and salt formation. These reactions may be accompanied by exothermic reaction which contributes to tissue injury. The lesions are deep with a thick eschar formation (Fig. 4.60). 

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