Hi Saira,
Thanks for getting in touch! There are a number of safe-wash oil based inks for relief printing, and there are broadly similar. All oil based inks are basically the same – they contain pigment, binder, and drier. Driers tend to be the hazardous component. The reason the Caligo safe wash inks are so safe, is that they have very little drier in them, less than 1%.
Pros
– they stay wet for a long time, so you can really take your time printing by hand, mixing inks, rolling out, etc.
– you can use them for monotypes, and have different inks rolled out for hours, and they will stay good
– you only need dish soap to wash up – use washing up gloves
– you can print wet-on-wet, or wet-on-semi-wet
Cons
– they take a long time to dry
– they emit a slightly linseedy smell
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Here is a link to Nick Morley’s giant whale lino cut, which he now prints entirely with a wooden spoon, using Caligo inks:
Giant Whale Linocut – Live Printing at London Illustration Fair 2017
Hope that helps!