The agency won the account after a one-off project brief earlier in the year.
The online retailer had previously taken its PR and comms activity in-house in March 2012.
The House PR team will work with comms director Victoria Chalmers, editorial director Newby Hands and beauty director Alice Manning, who recently joined the team from InStyle, to handle media relations and PR campaigns.
Dubbed the 'Net-A-Porter of beauty', feelunique.com is Europe's largest online beauty retailer and recently landed a £26m investment from Palamon Capital Partners and Sirius Equity.
The retailer has also been in talks with creative agencies as it seeks to improve its brand positioning.
Separately, House PR has also picked up the launch brief for FDD International's iWhite teeth whitening kit.
The agency will drive consumer awareness and sales of the kit, which is to be launched in 900 Boots stores in the UK this month.
The agency's beauty division also works for St. Tropez and Charles Worthington.