So eczema happens because your immune system is attacking it’s own layer of skin, in response to an allergy. It happens when your skin ins overly sensitive to the environment it’s in. It can develop as a result of allergies or disease. Lots of kids have eczema while their immune system is developing but then grow out of it, but scientists don’t really know why some people get it and others don’t.
Asthma is pretty similar, but happens in your windpipe.People who have asthma have overly-sensitive airways that react to particles more than they should, but scientists and medics still don’t know why this happens. You’re more likely to develop asthma if people in your family have it, and you definitely catch asthma from someone (like a cold, or the flu!). Luckily, some people grow out of it, but why, we still don’t know! There are theories that having a “too clean” environment means that when you’re exposed to these foreign particles you body reacts like it’s being attacked. Other scientists have found a possible genetic link, by identifying a chromosome alteration that seems to be common in asthmatic people. Fingers crossed for some answers soon!
And finally… impetigo! It’s a bit different to eczema – as impetigo is caused by a bacterial infection so it can be fought off with antibiotics. But people with eczema (and for some reason, people with diabetes) are more likely to get it.
Hope that answered all three of your questions hunterlo01!