A 2005 study by David Margolis, a dermatology professor at Penn, and others, found that acne patients given long-term antibiotic treatment, which often lasts more than 6 months, were more than twice as likely to have an upper respiratory tract infection during the year after treatment began than acne patients not given antibiotics.
Does this correlation reflect causality? Two additional analyses suggest it does:
1. Perhaps acne patients who get antibiotics are more likely to see a doctor than those who don’t. However, a study of patients diagnosed with high blood pressure, which also requires relatively frequent doctor visits, had the same risk of upper respiratory tract infections as acne patients not given antibiotics.
2. A later study found that the contacts of acne patients (such as their family) are more likely to have upper respiratory tract infections if the acne patient has such an infection — as you’d expect from contagion. But it makes no difference to these contacts if the acne patient was given antibiotics or not. This means that acne patients given antibiotics do not live in more infection-prone surroundings than acne patients not given antibiotics.
Bottom line: Support for the idea that the bacteria in our body help us stay healthy.