To the Editor: Cefaclor (Ceclor, Eli Lilly, Indianapolis, Ind.) is an oral cephalosporin recently introduced for the treatment of otitis media in children. In one clinical trial, cefaclor has been found equal in efficacy to amoxicillin in acute bacterial otitis media.1 The drug is reported to be effective in vitro against some beta-lactamase-producing strains of Haemophilus influenzae, but not against all.2 Few adverse reactions to this antibiotic have been reported.In metropolitan Lansing, Michigan, from November 1979 through June 1980, a generalized pruritic rash and arthritis (swelling and pain in both knee and ankle joints) developed in eight children . . .