Over 90% of outer ear infection is caused by bacterial infection, with 10% being fungal (and then, those are more liekly in tropical environments). The risk of fungal infection in non-tropical environments is thus fairly low probability.
There has also been several (4 that I can find myself) studies done on using acidic drops as the only treatment for ear infections, all which has shown them non-effective to clear an infection. Alcohol can also irritate the skin further, increasing inflammation.
Ear infections are however complex since most of the studies are either done on children, commercial or military divers. The military protocol in the Netherlands is to start with an acidic solution and then if the inflammation get worse introduce steroids. If that doesn't clear it, then add a combination of antibiotics and steroids. Steroids has the problem of increasing risk to bacterial infection, but the combination of using antibiotics with the steroids reduces that risk. It is this combination that doctors use in post surgery.
The Dutch protocol seems like the optimal treatment protocol for now, but it assumes you got a doctor to monitor it. My guess is that regular doctors jumps to the last step with the assumption that it is bacterial infection in order to minimize the need for further visits. One study I read also mentioned that adherence to correct application of the drops was one of the most significant factor in outcomes, which might imply an other reason to go for the strongest treatment first.
One thing that favors alcohol however is that keeping the ear dry is extremely important in addressing outer ear infection and preventing bacteria from growing. The theory behind vinegar and alcohol does thus seem quite sound from a theory perspective, stopping the bacterial infection before it get a chance to grow.
The US military does, or at least used to, use the alcohol/acid drops prophylactically - whenever you'd get out of the water you'd put some drops in.
It's interesting that the studies show that solution as ineffective. It cured my wife. Then someone at work had an outer ear infection that recurred after two treatments with antibiotic drops. This solution also solved their problem.
As a side note, my wife was on steroids when she contracted the infection. So I think that contributed to her catching it.
I am not aware of any study on prophylactically use, but I am cautiously hopefully that it work based on personal experience and from what I hear. For water sport activities, flushing with clean fresh water, dry it, and then spraying an acid solution seems to give some defense in keeping outer ear infections at bay. Alcohol could help drying it out, through because of the risk of triggering inflammation in the middle ear I personally avoid it.
I don't know why the studies shows them to be ineffective. Since they include acid drops in the studies it seems to be a well known home remedy, and given that it used prophylactically by the military in several countries there seems to be some reason for it. I could make a guess that doctors in the military/pediatric care are already keeping the ear of the patient dry so that alcohol don't provide any additional benefits, and they remove vax/debri in case those prevent the ear from drying.
There has also been several (4 that I can find myself) studies done on using acidic drops as the only treatment for ear infections, all which has shown them non-effective to clear an infection. Alcohol can also irritate the skin further, increasing inflammation.
Ear infections are however complex since most of the studies are either done on children, commercial or military divers. The military protocol in the Netherlands is to start with an acidic solution and then if the inflammation get worse introduce steroids. If that doesn't clear it, then add a combination of antibiotics and steroids. Steroids has the problem of increasing risk to bacterial infection, but the combination of using antibiotics with the steroids reduces that risk. It is this combination that doctors use in post surgery.
The Dutch protocol seems like the optimal treatment protocol for now, but it assumes you got a doctor to monitor it. My guess is that regular doctors jumps to the last step with the assumption that it is bacterial infection in order to minimize the need for further visits. One study I read also mentioned that adherence to correct application of the drops was one of the most significant factor in outcomes, which might imply an other reason to go for the strongest treatment first.
One thing that favors alcohol however is that keeping the ear dry is extremely important in addressing outer ear infection and preventing bacteria from growing. The theory behind vinegar and alcohol does thus seem quite sound from a theory perspective, stopping the bacterial infection before it get a chance to grow.