Frost blisters are pustular swellings due to the up-growth of callus-tissue into cavities caused by the uprising of the superficial cortex under the action of intense cold.
those due to .Synchytrium, Protomyces, Cysto pus, many Ustilagineae, &c. These cases are not easily distinguished superficially froni the pustular outgrowth of actual mycelia and spores (stromata) of such Fungi as Nectria, Puccinia, &c. The cylindrical stem-swellings due to Calyptospora, Epichloe, &c., may also be mentioned here, and the tyro may easily confound with these the layers and cushions of eggs laid on similar organs by moths.
When the true skin is inflamed various appearances may arise, according to the intensity and extent of the inflammation, and the eruption may be papular, vesicular, pustular, tubercular, bulbous or ulcerative.
contagious pustular dermatitis of sheep (orf ).
pustular psoriasis also can be generalized, covering most of the body.