The appointment is the result of J. Walter Thompson's successful pitch for a share of Reckitt's £300 million global advertising budget, settled three months ago.
The Manchester shop will be responsible for co-ordinating the global promotion of the Lemsip, Disprin, Gaviscon, Bonjela, Senokot and Fybogel brands above and below the line.
All are being switched from McCann-Erickson's Cheshire-based healthcare division, whose deputy managing director, David Donoghue, is among the six staff moving to CheethamBell to service the business.
Reckitt managers, who run the company's healthcare business out of their Hull headquarters, are understood to have asked the new agency to take on their team from McCann.
However, CheethamBell, which does not have a specialist healthcare unit, has no plans to establish one. Media remains with OMD.
Although JWT in London handles Boots business, including the company's medicines range, it is understood that Reckitt's decision to assign the business to CheethamBell was based on convenience rather than possible conflict.
The arrival of the healthcare business at CheethamBell makes Reckitt the agency's biggest client alongside Jaguar, for which it handles dealership support.