Has any of you had any experience with ear plugs at gigs? Can you tell me what I should look for when buying some?

I've never had problems at all with my ears, but in recent months I have had to call my doctor on numerous times to have eardrops, as post-gigs I wake up with watery liquid seeping out, and some swelling. Not nice!

I went to see Josephine Foster on Saturday, and remarkably woke up the next day with the same problems.... and she's all folky!

I've got Daniel Johnston at the weekend, and Joanna Newsom just after that, so I'm getting a bit concerned.

What should I be looking out for?