Guinea Pig Ear Swelling Test

Full Urticaria Cure

Full Urticaria Cure

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Predictive assays for evaluating the ability of materials to produce nonimmuno-logical contact urticaria have been developed. Lahti and Maibach (57) developed an assay in guinea pigs using materials known to produce urticaria in humans. One-tenth of a milliliter of the material (or control solvent) is applied to one ear of the animal. Ear thickness is measured before application and then every 15 min for 1 or 2 h after application. The maximum response is a 100% increase in ear thickness (within 50 min after application).

Materials can also be screened for nonimmunological contact urticaria in humans. A small amount of the test material is applied to a marked site on the forehead and the vehicle is applied to a parallel site. The areas are evaluated at about 20 to 39 min after application for erythema and/or edema (52).

Differentiation between nonspecific irritant reactions and contact urticaria may be difficult. Strong irritants (e.g., hydrochloric acid, lactic acid, and phenol), ^

can cause clear-cut immediate whealing if the concentration is high enough, but the reactions do not usually fade away quickly. Instead, they are followed by |

signs of irritation (erythema, scaling, or crusting) 24 h later. Some substances have only irritant properties (e.g., benzoic acid and nicotinic acid esters), some are pure irritants (e.g., SLS), and some have both these features [e.g., dimethyl «

sulfoxide (DMSO) and formaldehyde]. |

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