I had really bad eczema when I was a kid. Used to get slathered in coal tar ointment and wrapped in bandages every night before bed. Used to have to sit in front of a UV lamp for ages too. (Yes, primitive sounding treatments but this was in the 70s remember!) I also had really bad hay fever and allergies to about a million different things, including most animals, most washing powders and soaps, and most trees and flowers. Strangely, I've never really been allergic to any foods, apart from carrots which I always detested and which my parents used to puree and hide in other foods till they realised every time I ate them I projectile vomited everywhere...
By the time I hit my mid 20s my eczema had just about gone away, and my hay fever also calmed down tremendously. My dad says he was the same. I'm now 37 and I haven't had to take daily hay fever medication all through the summer for the last 5 years. And I only get the occasional patches of eczema breaking out round my eyes if I wear too much make up and don't clean it all off at night, and on my hands if I don't wear rubber gloves when washing the dishes.
I also had asthma from when I was about 16, but due to a combination of being very fit and only having very infrequent attacks, it was put down to my allergies and I wasn't properly diagnosed till I was 34 and had the worst attack ever and ended up in hospital one night just about half dead. Once I knew what it was I stopped smoking immediately and now I only have a mild attack maybe every six months or so.
Asthma, eczema, hay fever and allergies usually all go together, cause they're all caused by an over active auto-immune response, and yes, they usually run in families. Both sides of my family have tons of allergies and skin problems and my mum has multiple sclerosis which is the most horrible auto-immune condition of all.
I console myself with the fact that the worse over-active auto immune response a person has, the less likely they are to ever get cancer. This is due to your immune system being much better at 'zapping' cancer while it's still in the single-cell stages. The only person on both sides of my family who has had cancer was my dad's older brother, who smoked 80 a day from the age of 14 and still made it to 72!