Name: Robyn
Message: Is is safe to tie dye underwear, will the dye cause any problems to the skin or cause any unwanted infections??

It depends on the fiber and dye you use. There is no reported problem with the most popular type of dye for tie-dyeing, if it is used correctly, but some other dyes may cause problems.

The dyes used on polyester, acrylic, and acetate, known as Disperse dyes, are the most allergenic of dyes for the consumer, apparently because they gradually come off of the fiber, for the life of the garment. As a result, some people who are sensitive find that they do better wearing only natural fibers. (See the bottom of "Dyeing Polyester with Disperse Dyes".) There is also the issue of whether or not the fabric type traps excess moisture, thus encouraging infections, but that is another matter.

All-purpose dye contains Direct dye, which does not attach very firmly to the fiber, so there is a possibility that it might be absorbed and have similar effects, but I have not seen any medical journal articles suggesting that this actually happens.

The safest dye/fiber combination is fiber reactive dye (such as Procion MX, Cibacron F, or Drimerene K dye) on a cellulose fiber such as cotton. This is the type of dye recommended on my web site, e.g. in "How to Dye". These dyes form a permanent covalent bond with the cellulose fiber, and do not come off. People with chemical sensitivities have reported that they have no problems with properly made tie-dyes, made with Procion MX dye on cotton. It is very important, if this is a concern, to follow the dye instructions (don't forget soda ash aka sodium carbonate), and finish by washing first in cold water, and then in hot water until all excess, unattached dye is removed. To test whether all unattached dye has been washed out, press the damp cloth against some white fabric with a hot iron; if no color transfer occurs, the material is ready for use, even against sensitive skin.