Raw linseed oil is practically non-toxic. It has historically been used as a laxative. It is well absorbed through biological membranes such as the stomach and skin. Linseed oil can be irritating to the skin and is known to contain potent allergens. Cautions against the use of boiled linseed oil are common in health literature due to toxicological concerns about its additives. Thermopolymerized linseed oil (heated to high temperatures) may be toxic to the liver.
(http://www.greenconsumer.cc)

Walnut Oil, on the other hand, is a widely used food item, but a percentage of the population have allergic reactions to some or all nuts and nut products.

NOTE! If you have health concerns about your personal experience with either of these oils, you should consult your physician.

Walnut oil drys somewhat differently than linseed, sometimes a bit faster. M. Graham’s claims about faster drying might lead you to believe there’s a significant difference between the two. M. Graham walnut alkyd medium, though, probably does dry faster, but it is an alkyd, therefore a quite different critter from regular walnut oil.

cheers!

You can buy both linseed and walnut oil in health food stores (the linseed is labelled “flax seed oil”). The stuff used for paint is processed differently, but essentially the same. They are natural and non-toxic.

Metallic driers aren’t used to process Linseed so far as I know.
It is edible and completely safe, except for slight risk of possible allergies or psychosomatic reactions. Jim

I understand the processing of linseed oil for painting involves adding metallic dryers which might make it somewhat toxic.

Nope, not in the standard types.

“Boiled linseed oil” that you’d see in a hardware store will sometimes contain metallic driers though. These driers, if present, would tend to be highly toxic – cobalt and manganese are often used – but they’ll come with appropriate health warnings if they do.

Einion

I don’t recommend eating linseed or walnut oil sold for use in painting. If I happened to accidentally ingest a small amount, I wouldn’t worry unless it was specifcally labelled as containing driers or other toxic substances.

So is it OK to use the flax-seed oil from a health food shop for painting?

The largest “problem” with artist’s linseed is probably that it’s self-combustible. I know about fires caused by it. A rag with linseed can start burning without any specific fire-source, like a match or some other open fire. So it’s important to have a safe procedure for disposal of rags, and alike.

If you buy linseed oil, or walnut, in a food-store you wouldn’t know how weel-refined it is, or the general quality of it. Artist’s linseed oil doesn’t cost much if you buy a larger amount of it, so it’s not much to gain on buying it in food-stores.

Common sense says that one shouldn’t put artist’s linseed oil in food – for the same reasons – the producers aren’t making them for food, but for painting, so it may contain “something”, even if it normally won’t.

Some people may be allergic to linseed oil. As for that, if you get too much exposed to for instance normal detergents, you can develop allergies gradually. That’s not uncommon among people that make a living from washing. Nut-allergies are known to be outright dangerous.