Yeah, when I first looked into this, I found all these popular sites talking about tinnitus and infection, but couldn't track down any sources. Wikipedia just cites those websites. One actually does give a source: Journal of Hearing Sciences, 2006: 9-10. This seems to be made up by its "SEO professional" author. ("Journal of Hearing Science" at least exists, but started in 2011. Bizarre.)
I don't remember finding anything especially scientific and reliable on risks when I first looked into it. The best I could do was Ear Infection and the Use of Hearing Protection (1985), a review of epidemiological studies by a researcher employed by an earplug manufacturer, mostly concerning workplace use.
Anecdotal comments abound, but controlled studies are "conspicuous by their absence." By implication the problem is neither significant nor widespread; otherwise it would have drawn greater attention and research interest.
...
Although hearing protection devices should not be worn in the presence of some preexisting ear canal pathologies, and care must be exercised regarding selection and use under certain environmental conditions, regular wearing of HPDs does not normally increase the likelihood of contracting otitis externa.
I don't know how much you want to rely on that. I just follow the manufacturer's instructions for cleaning and reuse, and plan to stop if I notice irritation.
(Cross-posted from my personal site.)
Several months ago I began a list of "things to try," which I share at the bottom of this post. It suggests many mundane, trivial-to-medium-cost changes to lifestyle and routine. Now that I've spent some time with most of them and pursued at least as many more personal items in the same spirit, I'll suggest you do something similar. Why?
I removed the terribly personal items from my list, but what remains is still somewhat tailored to my own situation and habits. These are not recommendations; they are just things that struck me as having enough potential value to try for a week or two. The list isn't not remotely comprehensive, even as far as mundane self-experiments are concerned, but it's left as an exercise to the reader to find and fill the gaps. Take this list as an example or as a starting point, and brainstorm ideas of your own in the comments. The usual recommendation applies against going overboard in domains where you're currently impulsive or unreflective.
Related posts: Boring Advice Repository, Break your habits: Be more empirical, On saying the obvious, Value of Information: Four Examples, Spend money on ergonomics, Go try things, Don't fear failure, Just try it: Quantity trumps quality, No, seriously, just try it, etc.
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WORK ENVIRONMENT
WORK ROUTINE
LEISURE
COMMUTE
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