Curable silicone elastomer compositions having enhanced adhesive properties with respect to a wide variety of substrates are described. The compositions described herein are provided with a phenylmethylpolysiloxane based additive which comprises at least one, alternatively at least two Si—H groups per molecule and at least one, alternatively at least two epoxide functional groups per molecule. Said phenylmethylpolysiloxane based additives provide resulting elastomers with improved heat-humidity stabilization.