5 month old with congestion??

For a month or two now my 5 month old daughter has been suffering with congestion. I figured it was probable allergies since it mainly started when spring arrived. She was never a big spit up baby maybe a little bit now and then and she's never been a fussy baby she is always happy. Lately though she spits up a lot and even 30 mins to a hour after her feeding she will still spit up a lot of stuff. She still isn't fussy though. I thought again maybe it was allergies and congestion making her spit up. Last week she was very congested and a few days later developed a cough. So I took her to the pediatrician. Who decided her congestion was due to her having acid reflux and the spit up coming up her esophagus. Has anyone ever heard of anything like this? She wrote us a prescription for Zantac however I know nothing about the medicine and am not big on giving her medication unless absolutely necessary. I also know nothing about this gastroesphogal reflux... will she grow out of it? If I give her the medicine how long do I give it to her I don't want her to become dependent on it? Someone please help me!