selective toxicity- killing microbes w/o damaging the host, due to bacterial not having cell walls and having different ribosomes and having slightly different cellular metabolic procoess. fungi are all eukaryotes, meaning we cannot capitalize off of cellular differences, cells are more similar, there is more likely side effects, ringworm is fungi, zoonotic, very contagious, there is OTC, but topical is usually best bet because oral can have more side effetcs, viruses, most can attack things that are very virus specific, can attack replication process of viruses in our cell