advice please...

My daughter has a bit of a cough not bad but her nose had been running and yellow this morning. Doc said cough is from nasal drip and to use saline drops and it'll help. But she asked in prescription just in case. She said don't use unless it gets worse but she doesn't think I'll need to. It's aritromician (sp). She was going to give pcn but I said no bc I think she had a reaction last time even though the doc thought I was crazy. She had a rash that went away after she finished the meds. Anyway I hate giving antibiotics. But I don't want to do that wrong thing here. Is there anything else other than steam and nasal drops that may help her? She's about 25 weeks. Thanks!