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Skin irritation


In one patch test according to OECD guideline no.404, glyoxal (40 % aqueous solution) caused n irritation to rabbit skin after a 4-hour exposure as well as during the 72-hour observation period (BASF, 1985 c).


The acute skin irritation was examined in earlier studies on the shaven back skin of white rabbits in the patch test. Glyoxal was used as a 30 % or 40 % aqueous solution. The treatment times for the substance-covered cotton patches (ca. 2.5 cm x 2.5 cm ; no further details on the applied quantity) were 1, 5, 15 minutes and 20 hours. In addition, the rabbit ear was exposed for 20 hours. After an application period of 1,5 and 15 minutes, the treated skin was first washed with undiluted polyethylene glycol 400 and then with a 50 % aqueous polyethylene glycol 400 solution. The skin was not washed after the 20-hour treatment period. For an application period of 1 and 5 minutes, respectively, no or slight erythemas with a yellowing of the skin could be observed 24 hours after the exposure depending on the treatment time. With a treatment period of 15 minutes, a mild oedema was also noted. After 8 days, a yellowing and scaling of the skin at the application site was observed. The 20-hour exposure caused a slight, in some cases also a strong, erythema and oedema formation. After 8 days, a scaling of the skin, scab formation and a superficial necrosis were observed. The 20-hour exposure to the rabbit ear led to erythema and inflammation as well as to minor skin defects 24 hours after the application (no further details). After 8 days, scab formation and a slight necrosis were noted. No significant differences could be found between a 30 % and 40 % aqueous solution of pure glyoxal and a 40 % aqueous solution of raw glyoxal (BASF, 1956, 1963, a, b, 1970). Thus, slight to pronounced irritation could be seen, depending on the application period.


White adult rabbits (2 kg) obtained a 40 % glyoxal solution onto the shaven back skin (5 cm x 7 cm; no details on the administration period). From the third day a strong reddened inflammation, followed by a necrosis with tissue demarcation were observed. The changes almost completely disappeared 30 days later. The histopathological examination showed severe necrotic skin changes on the 4thday. These changes were less pronounced on the 9thday, and a regeneration of the epidermis was observed on the 18thday (Ito, 1963).


The application of 10 μl glyoxal (29,2 % aqueous solution) to the depilated abdominal skin of the rabbit caused a slight irritation (minor hyperaemia, irritation index 2 of 10 (Smyth et al., 1962)). Within the framework of an acute toxicity study (see Sect. 4.2), the single dermal administration (occlusive) of 1.57 ml 40 % aqueous glyoxal solution (corresponding to 798 mg glyoxal/kg body weight) to the shaven skin (dorsal, dorsolateral) of 5 Wistar rats/sex for an exposure period of 24 hours caused erythemas in all of the animals (BASF, 1985b).


In conclusion, after a four hour exposure patch test on rabbits (OECD guideline 404), glyoxal 40% caused no irritation. But taking into account studies by BASF where the duration of exposure is longer (up to 20 hours), glyoxal is clearly irritating to skin.


Eye irritation


In a study according to OECD guideline no. 405, 0.1 ml glyoxal (40 % aqueous solution) caused a definite reddening and chemosis of the conjunctiva of the rabbit eye (White Viennese, 1 male, 2 females) one hour after the instillation. After 24 hours, 2 animals exhibited a slight to definite chemosis of the conjunctiva. A slight conjunctival reddening and chemosis were still observed 72 hours after the administration. The symptoms completely subsided after 8 days (BASF, 1985c).


In another study on the irritating effect of glyoxal to the eye according to OECD guideline no. 405, glyoxal was likewise proven to be irritating (no further details (IFREB, 1982).


In earlier studies on the rabbit eye, the instillation of 50 μl glyoxal (30 % or 40 % aqueous solution) into the conjunctival sac caused a slight to strong reddening, mild oedemas, an inflammation as well as a hazy clouding of the cornea depending on the concentration. These changes completely healed within 1 or 2 weeks (BASF, 1956, 1963a,b).


In a comparative study between pure glyoxal (40 % aqueous solution) and raw glyoxal (40 % aqueous solution; no data on the impurities) on the rabbit eye, the instillation of 50 μl into the conjunctival sac caused a clear reddening and very strong inflammation on the conjunctiva. After installation of pure glyoxal, a temporary, hazy corneal clouding developed, while a milky clouding of the cornea and scarification on the upper eyelid resulted after instillation of raw glyoxal. Slight reddening and inflammation (pure product)and reddening, corneal clouding and scarification (raw product) were still observed 8 days after the administration (BASF, 1970).


In conclusion, the key study is the study by BASF (1985c) which conducted according to OECD guideline 405, showing that Glyoxal 40% is an eye irritant.

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