My 8 Yr Old Is Being Treated For Lyme Disease

My 8 yr old is being treated for Lyme Disease so she's on a # of different antibiotics and probiotics. Her Dr. Suggested she take oscillacocum (homeopathic) to treat her cold. She's had 4 doses between today and yesterday. Noting else seemed out of the ordinary. Tonight she has a red rash on her face and it was itchy but is now sensitive to touch. No fever, no other symptoms besides tongue tingling which scared me so I gave her some expired children's Benadryl (it was all I had but thought she might be having a reaction to something.) I've researched the internet but haven't found anything that matched. Is this serious?