This is a common subject for searches on this site extra page has been added with a really simple explanation. This is a technical subject, so this should be useful for anyone who might not be used to dealing with the complicated science. This is a technical subject, so this should be useful for anyone who might not be used to dealing with the complicated science. A more technical explanation is available here Ragwort Humans.
First of all the chemicals in Ragwort are not very poisonous. You would probably have to eat several pounds to really poison you.
These chemicals can pass through the skin but this has been studied and they don't pass through very well. In fact the studies in animals suggest that you you have to apply between twenty and fifty times more to get the same amount to actually get into your body than if you were to eat it.
It is probably best to wear gloves when handling plants not because of the poison in ragwort but because ragwort like many members of the daisy family has another set of chemicals which aren't poisonous but which can cause an itchy rash for a few days. Also you might be sensitive to other plants you might pick up by accident even if it is only a stinging nettle that you didn't see.
This information comes from reading scientific books and papers written by experts who have studied things and had their research checked by other experts before they were published. The chemicals in ragwort are actually present in lots of other flowers. About one in every thirty kinds of plant has them. One of these other plants has been used for many years as a herbal remedy to make ointments that are put on the skin. It doesn't seem to do any harm.
If you want more information there is also this website. Ragwort Facts and Myths . It is written by a Dutch woman. She was very concerned about ragwort until she asked some scientists about it. She realised that people were being frightened for no need and gathered up a list of scientists to help her write the site. She has had this special version of the site prepared in English.