It started in Dún Laoghaire with psoriasis and fake tan. Now two sisters and their team, who already won an Enterprise Ireland student entrepreneurship merit award in June, are competing to win one of the biggest student social entrepreneurship prizes in the world. Sadhbh and Aisling Wood’s father was looking for something that would stop the itching on his skin between steroid cream doses. Online research suggested coffee grounds might help – and he found that they worked well as an exfoliant to soothe the itching and to remove the dry, flaky skin. Along came his daughter Sadhbh with another problem.…