Synergistically uv-photoprotecting compositions comprising mixed screening agents

A regime or regimen for photoprotecting human skin and/or hair against the deleterious effects of ultraviolet irradiation, comprising topically applying thereon an effective amount of a cosmetic/dermatological composition which comprises synergistically UV-APPD-enhancing amounts of (a) particulates of at least one insoluble organic UV-screening agent having a particle size ranging from 10 nm to 5 μm, and (b) at least one UV-screening amino-substituted 2-hydroxybenzophenone compound having the following structural formula (I):

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• in which R1 and R2, which may be identical or different, are each a hydrogen atom, a C1-C20 alkyl radical, a C2-C10 alkenyl radical, a C3-C10 cycloalkyl radical or a C3-C10 cycloalkenyl radical, with the proviso that R1 and R2 can together form, with the nitrogen atom to which they are bonded, a 5- or 6-membered heterocyclic ring member;
• R3 and R4, which may be identical or different, are each a C1-C20 alkyl radical, a C2-C10 alkenyl radical, a C3-C10 cycloalkyl radical, a C3-C10 cycloalkenyl radical, a C1-C12 alkoxy radical, a (C1-C20) alkoxycarbonyl radical, a C1-C12 alkylamino radical, a di(C1-C12) alkylamino radical, an aryl radical or a heteroaryl radical which is optionally substituted, or a water-solubilizing substituent selected from among a carboxylate group, a sulfonate group or an ammonium residue;
• X is a hydrogen atom or a —COOR5 or —CONR6R7 radical;
• R5, R6 and R7, which may be identical or different, are each a hydrogen atom, a C1-C20 alkyl radical, a C2-C10alkenyl radical, a C3-C10 cycloalkyl radical, a C3-C10 cycloalkenyl radical, a —(YO)o—Z radical or an aryl radical;
• Y is —(CH2)2—, —(CH2)3—, —(CH2)4— or —CH—CH3—CH2—;
• Z is —CH2—CH3, —CH2CH2CH3, —CH2—CH2—CH2—CH3 or —CH(CH3)—CH3;
• m is an integer ranging from 0 to 3;
• n is an integer ranging from 0 to 3;
• o is an integer ranging from 1 to 2, formulated into (c) a topically applicable, cosmetically/dermatologically acceptable vehicle, diluent or carrier therefor.