A pharmaceutical composition comprising an effective amount of an Isoxazoline compound of formula wherein R 1 = halogen, CF 3, OCF 3, CN, n = integer from 0 to 3, preferably 1, 2 or 3, R 2 = C 1 -C 3 -haloalkyl, preferably CF 3 or CF 2 Cl, T = 5- or 6-membered ring, which is optionally substituted by one or more radicals Y, Y = methyl, halomethyl, halogen, CN, NO 2, NH 2 -C=S, or two adjacent radicals Y form together a chain, especially a three or four membered chain; Q= X-NR 3 R 4 or a 5-membered N-heteroaryl ring, which is optionally substituted by one or more radicals; X = CH 2, CH(CH 3), CH, CO, CS, R 3 = hydrogen, methyl, haloethyl, halopropyl, halobutyl, methoxymethyl,methoxyethyl, halomethoxymethyl, ethoxymethyl, haloethoxymethyl, propoxymethyl, ethylaminocarbonylmethyl, ethylaminocarbonylethyl, dimethoxyethyl, propynylaminocarbonylmethyl, N-phenyl-N-methyl-amino, haloethylaminocarbonylmethyl, haloethylaminocarbonylethyl, tetrahydrofuryl, methylaminocarbonylmethyl, (N,N-dimethylamino)-carbonylmethyl, propylaminocarbonylmethyl, cyclopropylaminocarbonylmethyl, propenylaminocarbonylmethyl, haloethylaminocarbonylcyclopropyl, wherein Z A = hydrogen, halogen, cyano, halomethyl (CF 3); R 4 = hydrogen, ethyl, methoxymethyl, halomethoxymethyl, ethoxymethyl, haloethoxymethyl, propoxymethyl, methylcarbonyl, ethylcarbonyl, propylcarbonyl, cyclopropylcarbonyl, methoxycarbonyl, methoxymethylcarbonyl, aminocarbonyl, ethylaminocarbonylmethyl, ethylaminocarbonylethyl, dimethoxyethyl, propynylaminocarbonylmethyl, haloethylaminocarbonylmethyl, cyanomethylaminocarbonylmethyl, or haloethylaminocarbonylethyl; or R 3 and R 4 together form a substituent selected from the group consisting of: or a salt or solvate thereof and a pharmaceutically acceptable carrier for use in the prevention or treatment of parasitic mite infestations of laying hens that are producing eggs for human consumption, wherein the composition is diluted in one or more steps with water to form medicated drinking water, that is administered in two separate dosages 7 days or 14 apart, each of them contain 50 % of the dose. R 1 = halogen, CF 3, OCF 3, CN, n = integer from 0 to 3, preferably 1, 2 or 3, R 2 = C 1 -C 3 -haloalkyl, preferably CF 3 or CF 2 Cl, T = 5- or 6-membered ring, which is optionally substituted by one or more radicals Y, Y = methyl, halomethyl, halogen, CN, NO 2, NH 2 -C=S, or two adjacent radicals Y form together a chain, especially a three or four membered chain; Q= X-NR 3 R 4 or a 5-membered N-heteroaryl ring, which is optionally substituted by one or more radicals; X = CH 2, CH(CH 3), CH, CO, CS, R 3 = hydrogen, methyl, haloethyl, halopropyl, halobutyl, methoxymethyl,methoxyethyl, halomethoxymethyl, ethoxymethyl, haloethoxymethyl, propoxymethyl, ethylaminocarbonylmethyl, ethylaminocarbonylethyl, dimethoxyethyl, propynylaminocarbonylmethyl, N-phenyl-N-methyl-amino, haloethylaminocarbonylmethyl, haloethylaminocarbonylethyl, tetrahydrofuryl, methylaminocarbonylmethyl, (N,N-dimethylamino)-carbonylmethyl, propylaminocarbonylmethyl, cyclopropylaminocarbonylmethyl, propenylaminocarbonylmethyl, haloethylaminocarbonylcyclopropyl, wherein Z A = hydrogen, halogen, cyano, halomethyl (CF 3); R 4 = hydrogen, ethyl, methoxymethyl, halomethoxymethyl, ethoxymethyl, haloethoxymethyl, propoxymethyl, methylcarbonyl, ethylcarbonyl, propylcarbonyl, cyclopropylcarbonyl, methoxycarbonyl, methoxymethylcarbonyl, aminocarbonyl, ethylaminocarbonylmethyl, ethylaminocarbonylethyl, dimethoxyethyl, propynylaminocarbonylmethyl, haloethylaminocarbonylmethyl, cyanomethylaminocarbonylmethyl, or haloethylaminocarbonylethyl; or R 3 and R 4 together form a substituent selected from the group consisting of: or a salt or solvate thereof and a pharmaceutically acceptable carrier for use in the prevention or treatment of parasitic mite infestations of laying hens that are producing eggs for human consumption, wherein the composition is diluted in one or more steps with water to form medicated drinking water, that is administered in two separate dosages 7 days or 14 apart, each of them contain 50 % of the dose.