I started swimming around the month of May and had ear problems twice. I started using ear plugs -- Aqua Sphere -- and this has helped. I started wearing a cap as of yesterday.
I had a slight reoccurrence of redness last week and just stayed out of the pool until yesterday. I also put drops in my ear afterwards. I use Swim Ear that I got from a grocery store.
I'm trying different things before I have to change the amount of time that I spend in the pool. Next steps are to see a specialist and then change where I swim (in case the place that I swim has unusually dirty water).