What is the natural remedy that can be used as an antibiotic ?

I tend to get sick a lot mostly from bacteria (infection), allergy, mold, etc. Of course I am careful and try to keep the place allergy / mold free home. Whenever I get sick (bacteria infection / sinus infection / upper respiratory infection ) Conventional doctor would give me an antibiotic and I am feeling better in about 10 days. Fine. But I also know the downside of using antibiotic. What are the healthier better alternate ?