Abstract: Provided is a formulation that can improve all of transdermal absorbability of an active ingredient, immediate effect in transdermal absorption, and reduction of skin irritation, to high levels. A formulation containing: a base; and a core-shell structure having a core portion containing an active ingredient and a shell portion containing a surfactant; in which the core portion is a solid, the surfactant contains a compound having two or more fatty acid bonds and a compound having one fatty acid bond, and a proportion of the compound having two or more fatty acid bonds in the surfactant is 5% by weight or more and 75% by weight or less.

Abstract: Provided is a core-shell structure that can achieve both improvement in transdermal absorption of an active ingredient and reduction in skin irritation at a high level. A core-shell structure 10 includes: a core portion 11 containing an active ingredient, the core portion being solid; and a shell portion 12 containing both a first surfactant having a melting point of less than 35° C. and a second surfactant having a melting point of 35° C. or more, the first surfactant and the second surfactant each having an HLB value of 4 to 14, the first surfactant and the second surfactant each containing at least one selected from the group consisting of sorbitan fatty acid esters, glycerin fatty acid esters, propylene glycol fatty acid esters, and fatty acid alkanolamides.

Abstract: Provided is an external skin preparation capable of enhancing permeability of an active ingredient into parts of the epidermis located below the stratum corneum and the dermis even when a poorly water-soluble active ingredient is used. There is provided an external skin preparation containing a core-shell structure, comprising a core portion containing a poorly water-soluble active ingredient and a solubilizing agent, and a shell portion containing a surfactant. The solubilizing agent is at least one selected from the group consisting of cyclodextrin, methyl-cyclodextrin, dimethyl-cyclodextrin, 2-hydroxypropyl-cyclodextrin, hydroxyethyl-cyclodextrin, sulfobutyl ether-cyclodextrin, glucosyl-cyclodextrin, maltosyl-cyclodextrin and cluster dextrin. The surfactant is at least one selected from the group consisting of glycerol fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters and fatty acid alkanolamides.

Abstract: Provided is a core-shell structure having an excellent immediate effect in transdermal absorption of an active ingredient. A core-shell structure comprising a core portion containing an active ingredient, and a shell portion containing a surfactant having an HLB value of 4 to 14, the core portion being solid, and the surfactant containing a saturated hydrocarbon group having 7 to 15 carbon atoms or an unsaturated hydrocarbon group having 7 to 17 carbon atoms.

Abstract: Provided is an external skin preparation capable of enhancing permeability of an active ingredient into parts of the epidermis located below the stratum corneum and the dermis even when a poorly water-soluble active ingredient is used. There is provided an external skin preparation comprising a poorly water-soluble active ingredient and a solubilizing agent, wherein the solubilizing agent is at least one selected from the group consisting of water-soluble polymers, water-soluble saccharides, water-soluble surfactants and aromatic carboxylic acids.

Abstract: A particle comprising a first fraction containing an active ingredient and a second fraction containing a surfactant, and having a number average particle diameter of from 1 to 100 nm.

Abstract: The present invention provides a core-shell structure having high skin permeability. The core-shell structure includes a core portion containing a hydrophilic drug having a molecular weight of 400 or more; and a shell portion containing a surfactant, and the core portion is a solid, the hydrophilic drug has a water-octanol partition coefficient of ?3 or more and 6 or less, the surfactant has an alkyl group or an alkenyl group having 10 to 20 carbon atoms, and a mass ratio between the hydrophilic drug and the surfactant (hydrophilic drug:surfactant) is 1:5 to 1:20.

Abstract: Problem to be Solved There is provided a formulation including a particle containing an active ingredient and a surfactant, wherein morphological stability is excellent. Solution A particle containing an active ingredient, a surfactant and a pH adjuster.

Abstract: Provided are an active ingredient-containing particle with improved shape retainability. The particle includes a first fraction containing an active ingredient, a second fraction containing a surfactant, and at least one water-soluble polymer selected from the group consisting of a polysaccharide and a polymer having 2-methacryloyloxyethyl phosphorylcholine as a constituent unit.

Abstract: Provided is a core-shell structure having an excellent immediate effect in transdermal absorption of an active ingredient. A core-shell structure comprising a core portion containing an active ingredient, and a shell portion containing a surfactant having an HLB value of 4 to 14, the core portion being solid, and the surfactant containing a saturated hydrocarbon group having 7 to 15 carbon atoms or an unsaturated hydrocarbon group having 7 to 17 carbon atoms.

Abstract: An object is to provide a formulation that includes a particle containing an active ingredient and a surfactant, and a base, and is more excellent in storage stability. For solution, a formulation including a particle containing an active ingredient and a surfactant, and a base, in which the surfactant is contained in a ratio of 5 to 100 parts by weight based on 1 part by weight of the active ingredient, is provided.

Abstract: Provided are an active ingredient-containing particle with improved shape retainability. The particle includes a first fraction containing an active ingredient, a second fraction containing a surfactant, and at least one water-soluble polymer selected from the group consisting of a polysaccharide and a polymer having 2-methacryloyloxyethyl phosphorylcholine as a constituent unit.

Abstract: An object of the present invention is to prevent a particle including a first fraction containing an active ingredient and a second fraction containing a surfactant from bleeding out from the base phase of an external preparation. The external preparation comprises a particle including a first fraction containing an active ingredient and a second fraction containing a surfactant, and a base phase containing a gelatinous liquid component.

Abstract: The present invention provides a core-shell structure having high skin permeability. The core-shell structure includes a core portion containing a hydrophilic drug having a molecular weight of 400 or more; and a shell portion containing a surfactant, and the core portion is a solid, the hydrophilic drug has a water-octanol partition coefficient of ?3 or more and 6 or less, the surfactant has an alkyl group or an alkenyl group having 10 to 20 carbon atoms, and a mass ratio between the hydrophilic drug and the surfactant (hydrophilic drug:surfactant) is 1:5 to 1:20.

Abstract: A particle comprising a first fraction containing an active ingredient and a second fraction containing a surfactant, and having a number average particle diameter of from 1 to 100 nm.

Abstract: An object is to provide a formulation that includes a particle containing an active ingredient and a surfactant, and a base, and is more excellent in storage stability. For solution, a formulation including a particle containing an active ingredient and a surfactant, and a base, in which the surfactant is contained in a ratio of 5 to 100 parts by weight based on 1 part by weight of the active ingredient, is provided.