Girls, I recently wrote that the baby had a fever with no other sympto…

Girls, I recently wrote that the baby had a fever with no other symptoms, I thought it might be toothache. Many people wrote that it could be roseola. Yesterday I saw a doctor who checked and said it was otitis (ear), she prescribed an antibiotic, yesterday gave it for the first time, in the morning it broke out. Could this be a side effect? Has anyone experienced side effects from antibiotics?!