Aldara cream can delay the return of cold sores, but it can cause severe inflammation, according to a report in the journal Clinical Infectious Diseases.Studies in guinea pigs found the cream reduced sore formation during and after treatment, Dr. David I. Bernstein of the Cincinnati Children’s Hospital Medical Center and colleagues note. He and his colleagues hypothesized that Aldara (generic name, imiquimod) could boost the body’s defenses against the herpes virus, which causes cold sores, and delay the return of the lesions.To investigate, they compared Aldara with an inactive “vehicle” cream in 47 patients with recurrent cold sores. Study participants applied the cream within 48 hours after the reappearance of a lesion and then again a few days later.Subjects who used Aldara reported more severe redness, swelling, scabbing, pain and burning, in some cases occurring after the application of the first dose. Treatment was halted early due to severe side effects in five patients treated with Aldara.