An extract from inflamed skins of rabbits inoculated with vaccinia virus is provided where the quality of the extract is more stabilized. A preparation, etc. containing said extract as an active ingredient is also provided. When the amount of sulfated tyrosine contained in an extract from inflamed skins of rabbits inoculated with vaccinia virus and also contained in a preparation containing said extract as an active ingredient is used as an index, the quality of the extract and the preparation among the manufacturing lots can be warranted as a more stabilized one. In the extract from inflamed skins of rabbits inoculated with vaccinia virus and the preparation containing said extract where the quality thereof is more stabilized by such a method, the efficacy and the safety thereof are now guaranteed more strictly resulting in very high usefulness.