Question

why antibiotics are not effective against viral infections ?

Answer 1

Antibiotics kill bacteria by recognizing the antibodies secreted by the bacteria, then attach themselves to the bacteria and give out a signal calling for white blood cells (phagocytes) to eat up the bacteria. Viruses do not secrete the antibodies recognized by antibiotics as they do not resemble proper cells, therefore antibiotics cannot recognize viruses and thus they cannot be digested by phagocytes.

Answer 2

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It's not effective against viruses because they're totally different from bacteria.
Antibiotics kill bacteria in several ways, like inhibition of cell wall synthesis, DNA replication, Protein synthesis. Viruses do not have cell walls, they do not replicate their dna and they don't synthesize proteins. So antibiotics have no mechanism to kill viruses. There are drugs that kill or inhibit viruses, they're called antiviral drugs. An example is acyclovir.

@iceicebaby I don't know where you got that answer but i have never heard about the ability of antibiotics to recognize antibodies. I think you must mean some lymphocyte, they recognize antibodies.

Answer 3

It was copied & pasted from this page:
http://wiki.answers.com/Q/Why_the_antibiotics_are_ineffective_against_viral_diseases

Answer 4

In a general sense, certain viral infections are immune to certain or all antibiotics. However, it depends on the viral infection. As you may know, certain viral infections come in various strain types. In such case, each strain type is resistant to a certain or all antibiotic.