shatnez is the biblical prohibition against wearing wool and linen together in the same garment. (Wearing one piece of clothing that is linen and another that is wool at the same time is permitted.) This prohibition against shatnez is found in Deuteronomy 22:11 and Leviticus 19:19. A combination of any other materials does not create shatnez.

The reference to wool refers to wool from sheep or lambs. It does not refer to camel wool, mohair, angora, cashmere, alpaca or vicuna. The reference to linen applies only to fibers from the flax plant, not hemp or jute. However, reprocessed fibers may also contain shatnez.

The prohibition also includes any combination of wool and linen, regardless of whether the two are combined in one cloth or are separate pieces of cloth within the same garment. Even suits that are 100% synthetic may contain shatnez. American law allows some leeway in labeling. A label that states that a garment is 100% wool may contain as much as 2% of other materials. In addition, the label refers to the fabric, not any threads or material in the padding and ornamental trim. According to experts in the field, shatnez is more likely to occur in European clothing than in clothing made in the United States or Canada.

The prohibition applies not only to suits, coats, dresses and pants, but to any type of clothing, including socks, pajamas, gloves and ties. It is also forbidden to wear a garment in which an ornamental part, such as a tassel that does not touch the body, has shatnez. However. it is permitted to try on a garment in a clothing store without knowing whether it has shatnez or not. If the label clearly states that the garment includes both wool and linen, then it is prohibited.

Why Such a Law?

A common place for shatnez to be found is under the collar of high-end suits
A common place for shatnez to be found is under the collar of high-end suits

The law prohibiting shatnez falls into the category of what is known as a chok, a law that cannot be explained. Various reasons have been suggested, however. The explanation given by Maimonides is that pagan priests were required to wear garments made of wool and linen. The prohibition may have been established to separate Jews from pagan practices. It is interesting to note, however, that the clothing of the priests in the Temple was exempt from this prohibition, giving rise to an alternate explanation, that the prohibition was designed to separate priestly from public practice.

Another and more colorful explanation is that Abel brought wool as an offering, whereas Cain brought flax. The mixture was lethal and Abel lost his life.

A more esoteric explanation is that everything has its own spiritual force. By mixing certain items together, these forces are compromised and cannot perform their assigned task.

The shatnez Checkers of Today

From two verses in the Torah, plus the complexities of modern clothing manufacturing, there has arisen an international service to test for shatnez.

Since clothing labels cannot be relied upon, there must be another way in which to determine whether or not an article of clothing contains shatnez. The answer is the shatnez sample taker, and the shatnez tester in the shatnez laboratory. The sample takers are trained to take appropriate samples from a garment (without damaging the garment) and to send the samples to the shatnez laboratory. At the laboratory, shatnez testers examine the sample under a low-powered (about 100X) microscope, either binocular or monocular, and are able to identify the fibers.

Laboratories exist in most major Jewish communities in North America. Most of the laboratories do not operate full-time, but have a reasonable short turnaround time of a few days. They also will receive and return garments by courier or regular mail. It is rare that a laboratory is not able to determine if a garment is shatnez.

There is no doubt that with the widespread use of synthetic fabrics, the issue of shatnez is not as prominent as it once was. However, the issue still arises, especially since many garments are manufactured in various parts of the world, in some cases with parts of a garment being manufactured in one country and parts in another. The result is that it is difficult for consumers to know everything that is in that garment. New fabrics are also being developed, as are new combinations of fabrics.

Considering these developments. the shatnez testers of America and their contacts in other countries have an informal network by which alert notices are sent out as new developments are discovered. This is all part of a vibrant support system that has been developed around this ancient and mysterious prohibition.