A skin treatment composition comprising a Mahonia aquifolium extract in a liposome delivery system. The Mahonia aquifolium extract is present in the skin treatment composition in a range of from 5% to 20% by weight of the total composition. The skin treatment composition is particularly effective in the treatment of psoriasis, eczema and other dry skin conditions. The invention further provides a process for obtaining an extract of Mahonia aquifolium.