3 yo is on amoxicillin for strep, 5 days now. but she has lesions that look like hand, foot, mouth. do i keep giving her the antibiotics?

Confirmed strep ?: If the strep was confirmed by office testing before treatment, you should finish treatment. If your treatment source looked at the throat and just treated assuming it was strep, call them and discuss your options.A kid can have both illnesses at the same time and finishing the antibiotic would not hurt the course of hfm.

Until re-evaluated: Take the medications as prescribed by the provider originally, until you call them and can get your child in for an evaluation and assessment of their condition, to be properly diagnosed, so the best and most appropriate treatment will be given moving forward. Best wishes.

Yes: Yes, absolutely. If she tested positive for group a strep, she definitely needs to finish the full course of antibiotics to prevent complications such as rheumatic fever and glomerulonephritis (kidney inflammation). Strep can produce lesions in the mouth, particularly on the soft palate and on the tonsils. Unless she was exposed to other children with hfm, it's more likely the strep causing it.

7 days management: The antibiotics will not treat the virus causing hand, foot and mouth disease, but it is possible to have both strep A and a viral infection at the same time. I would advise finishing a 7 day course of Amoxicillin. By day 10 the symptoms should resolve. I hope that she feels better.