Presumably Dr. Jenny Kim is a good dermatologist because the author of this NPR piece chose to quote her:
UCLA dermatologist Dr. Jenny Kim says many people don’t realize it’s bacteria that cause acne. “Some people say your face is dirty, you need to clean it more, scrub more, don’t eat chocolate, things like that. But really, it’s caused by bacteria and the oil inside the pore allows the bacteria to overpopulate,” Kim says.
If I were to ask Dr. Kim how she knows that acne is “caused by bacteria” I think she’d say “because when you kill the bacteria [with antibiotics] the acne goes away.” Suppose I then asked: “Is there evidence that the bacteria of people who get acne differ from the bacteria of people who don’t get acne (before the acne)?” What I assume Dr. Kim would answer: “I don’t know.”
There is no such evidence, I’m sure. It is quite plausible that the bacteria of the two groups (with and without acne) are exactly the same, at least before acne. If it turned out, upon investigation, that the bacteria of people who get acne is the same as the bacteria of people who don’t get acne, that would make it much harder to say that acne is caused by bacteria. As far as I can tell, Dr. Kim and apparently all influential dermatologists have not thought even this deeply about it. To do so would be seriously inconvenient, because if acne isn’t caused by bacteria, it would be harder to justify prescribing antibiotics. Which dermatologists have been doing for decades.
It isn’t just dermatologists. Many doctors believe that H. pylori causes ulcers wasn’t a Nobel Prize given for discovering that? The evidence for that assertion consisted of: 1. H. pylori found at ulcers. 2. Doctor swallowed billions of H. pylori and didn”t get an ulcer. (Not a typo.) It was enough that he got indigestion or something. 3. Antibiotics cause ulcers to heal. That was enough for the two doctors who made the H. pylori case and the Nobel Prize committee they convinced. The doctors and the committee failed to know or understand that H. pylori infection is very common and almost no one who is infected gets an ulcer. Psychiatric causal reasoning has been even simpler and even more self-serving. We know that depression a huge problem is due to “a chemical imbalance”, according to many psychiatrists, because (a) antidepressants work (not very well) and (b) antidepressants change brain chemistry.
Dr. Kim’s false certainty matters because I’m sure most people with acne don’t know what causes it. I didn’t. Dr. Kim’s false certainty and similar statements from other dermatologists make it harder for them to find out. I wrote about a woman who figured out what caused her acne . It wasn’t easy or obvious.