Irwin McLean is investigating the genetic basis of inherited skin diseases. His primary interest lies in the gene that encodes filaggrin, a protein that binds to keratin fibres in epithelial cells and plays a significant role in maintaining the hydration and barrier function of the skin.

Mutations in the filaggrin gene — found in 10 per cent of the UK population — hinder the production of filaggrin protein and lead to a dry, flaky skin condition known as ichthyosis vulgaris. Irwin showed that people with such mutations are at much greater risk of developing atopic eczema and other allergic diseases; without filaggrin, the skin is a less effective barrier to pathogens, allergens and irritants — triggering an immune response.

Additionally, Irwin has identified the individual genes that cause over 20 other disorders affecting epithelial cells and tissues, including the skin. He is also heavily involved in small molecule drug discovery and is developing new RNA-based therapies to treat some of these previously identified disorders.