Although topical products with antibiotic properties can be purchased without a prescription, no over-the-counter antibiotics for internal use are allowed in the United States. Other countries follow different practices and allow some antibiotics to be purchased without a prescription, but the strongest drugs are generally never available over-the counter. The primary reason for restrictions on over-the-counter antibiotics is the prevention of antibiotic overuse and misuse, to limit unnecessary side effects, and to slow the emergence of antibiotic resistance in bacteria.
Antibiotics are only useful in treating bacterial infections, such as strep throat or tuberculosis. They are of no use in dealing with viral infections, such as colds and influenza. Consumers, however, do not always understand the difference between viruses and bacteria, and will often seek to purchase and use antibiotics when they are suffering from viral infections.
All of these drugs work by attacking and killing or weakening bacteria, but this process is never perfect, and not all bacteria exposed to an antibiotic will die. Usually, the immune system of a patient being treated with an antibiotic will be able to finish the job, and no bacteria with resistance to the antibiotic being used will survive.
Each time an antibiotic is used, however, there is some chance that bacteria with resistance to that drug will survive. These bacteria can then pass on their immunity to their offspring, and eventually, the entire bacterial population will be either resistant or immune to antibiotics that were once effective against it. Over-the-counter antibiotics are restricted in the United States in order to minimize the rate at which bacteria can develop antibiotic resistance.
Serious side effects can also occur with antibiotic use. Since antibiotics are, in essence, toxins, they do damage directly to the human body while they are fighting bacterial infection. Antibiotics are formulated so that they will do enough damage to bacteria to remove an infection but will not generally permanently harm a human, but there are still risks associated with antibiotic use. For example, a normal human body contains populations of symbiotic microbes, most notably in the digestive tract, and antibiotics can kill these, causing intestinal distress.
Topical antibiotics are an exception to the general ban on over-the-counter antibiotics in the United States. Since they act mostly outside of the body, these antibiotics can be much stronger than those taken internally, and side effects are less of an issue. These topical over-the-counter antibiotics should never be taken internally.