Yes, more likely allergies rather than dogs - I can't see how eczema would be made worse by dogs, but I suppose it's not unreasonable. There's probably all sorts of other chemicals around that are more likely though!
My 3 year old has eczema she has a severe case of it.It depends on what you are allgeric to. Your allergies is what can cause the flare up's my daughter is allgeric to cat's she has no problem's with dog's we have one in the house.Has your sister ever had allergie testing on them to see what may cause it.Eczema you can't catch from anyone or any animal it is something you are born with it can be passed down through generations.We tested my daughter and found out she was allergic to alot of thing's including apples if she was to eat them she would get hives witch was from being allgeric but the itching from being allergic would calls her eczema to flare up.So if your sister hasn't had them tested to see if they were allgeric to dog's and they had no sign's of itching when they were around them then i would say they would be find.
Doesn't sound right, pets may cause allergies and asthma but never heard of them causing eczema.
A good site for info on childhood eczema is www.exederm.com