There are 2 groups of Permanent Makeup pigments.
Iron Oxide
Non-Iron Oxide
Iron oxides have been one of the most commonly used coloring agents for cosmetics for over a century. They have also been used in foods and medications. In the permanent Makeup world using iron oxides are essential because iron is the most stable and the most common of all of the elements. It’s nontoxic and has a variety of colors available to technicians. Iron oxides are inert, innocuous and non-reactive. In other words, they are safe, harmless and inactive. It is almost unheard of that any one has an allergic reaction to iron oxides. The metal content is way below the FDA’s list of approved colorants.
Iron oxide can limit options if removal is necessary. If your Permanent Makeup needs to be redesigned because of bad shape or improper placement, it is more difficult to change, adjust, correct or remove the ink from your skin.
The non-iron (organic) pigments usually fade off without any traces as though they were never there in the first place, which is important when permanent makeup needs to be redesigned. The worse thing that happens with non-iron oxide pigments is that warm brow colors turn ashy over the years as it is fading off, but with a touch up this is easily corrected. Lips fade off without much change other than becoming a lighter version of the original. With the eyes, as the years go by the black eyeliner can have a tinge of blue under certain lighting as it is fading off, but with a color touch up you can just restore the color.
Reputable manufactures of high-quality iron oxide and reputable manufactures of non-iron oxide permanent makeup pigments both have been proven to be safe, long lasting and fade resistant. Using low quality pigments can cause undesirable permanent makeup colors. It is important that your technician use a reputable, safe, predictable, and true to color pigment manufactures.
I do use both iron oxide pigments and non-iron oxide pigments. Like everything in life there are exceptions to the rules, and sometimes it is more acceptable to use organic ink on the client instead of iron oxide ink.
Lastly, the technician should understand color theory to help prevent undesirable color changes from happening with any high quality pigments.