Embroidery thread is yarn

Yarn

Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery and ropemaking. Thread is a type of yarn intended for sewing by hand or machine. Modern manufactured sewing threads may be finished with wax or...

 that is manufactured or hand-spun

Spinning (textiles)

Spinning is a major industry. It is part of the textile manufacturing process where three types of fibre are converted into yarn, then fabric, then textiles. The textiles are then fabricated into clothes or other artifacts. There are three industrial processes available to spin yarn, and a...

 specifically for embroidery

Embroidery

Embroidery is the art or handicraft of decorating fabric or other materials with needle and thread or yarn. Embroidery may also incorporate other materials such as metal strips, pearls, beads, quills, and sequins....

 and other forms of needlework

Needlework

Needlework is a broad term for the handicrafts of decorative sewing and textile arts. Anything that uses a needle for construction can be called needlework...

.

Threads for hand embroidery include:

• Embroidery floss or stranded cotton is a loosely twisted, slightly glossy
  Gloss (material appearance)
  Gloss is an optical property, which is based on the interaction of light with physical characteristics of a surface. It is actually the ability of a surface to reflect light into the specular direction. The factors that affect gloss are the refractive index of the material, the angle of incident...
  
   6-strand thread, usually of cotton
  Cotton
  Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
  
   but also manufactured in silk
  Silk
  Silk is a natural protein fiber, some forms of which can be woven into textiles. The best-known type of silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity...
  
  , linen
  Linen
  Linen is a textile made from the fibers of the flax plant, Linum usitatissimum. Linen is labor-intensive to manufacture, but when it is made into garments, it is valued for its exceptional coolness and freshness in hot weather....
  
  , and rayon
  Rayon
  Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers, it is neither a truly synthetic fiber nor a natural fiber; it is a semi-synthetic or artificial fiber. Rayon is known by the names viscose rayon and art silk in the textile industry...
  
  . Cotton floss is the standard thread for cross-stitch
  Cross-stitch
  Cross-stitch is a popular form of counted-thread embroidery in which X-shaped stitches in a tiled, raster-like pattern are used to form a picture. Cross-stitch is often executed on easily countable evenweave fabric called aida cloth. The stitcher counts the threads in each direction so that the...
  
  . Extremely shiny rayon floss is characteristic of Brazilian embroidery
  Brazilian embroidery
  Brazilian embroidery is a type of surface embroidery that uses rayon thread instead of cotton or wool. It is called "Brazilian" embroidery because the use of high-sheen rayon thread in embroidery was first popularized in Brazil, where rayon was widely manufactured. Brazilian embroidery patterns...
  
  .
• Perle cotton, pearl cotton, or French coton perlé is an S-twisted, 2-ply thread with high sheen, sold in five sizes or weights (No. 3, 5, 8, 12 and 16 (Finca), with 3 being the heaviest and 16 the finest).
• Matte embroidery cotton or French coton à broder is a matte-finish (not glossy) twisted 5-ply thread.
• Medici or broder medici is a fine, light-weight wool thread formerly manufactured by DMC Group.
• Crewel yarn is a fine 2-ply yarn of wool
  Wool
  Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, camel from animals in the camel family, and angora from rabbits....
  
   or, less often, a wool-like acrylic
  Acrylic fiber
  Acrylic fibers are synthetic fibers made from a polymer with an average molecular weight of ~100,000, about 1900 monomer units. To be called acrylic in the U.S, the polymer must contain at least 85% acrylonitrile monomer. Typical comonomers are vinyl acetate or methyl acrylate...
  
  .
• Persian yarn is a loosely twisted 3-strand yarn of wool or acrylic, often used for needlepoint
  Needlepoint
  Needlepoint is a form of counted thread embroidery in which yarn is stitched through a stiff open weave canvas. Most needlepoint designs completely cover the canvas...
  
  .
• Tapestry yarn or tapestry wool is a tightly twisted 4-ply yarn.

Threads for machine embroidery

Machine embroidery

Machine embroidery is an embroidery process whereby a sewing machine or embroidery machine is used to create patterns on textiles. It is used commercially in product branding, corporate advertising, and uniform adornment. Hobbyists also machine embroider for personal sewing and craft projects.There...

 are usually of polyester

Polyester

Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...

 or rayon (less often cotton or silk).

Threads, like textiles, can contain compounds that may be harmful to humans. Many dye

Dye

A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....

s have been shown to be allergen

Allergen

An allergen is any substance that can cause an allergy. In technical terms, an allergen is a non-parasitic antigen capable of stimulating a type-I hypersensitivity reaction in atopic individuals....

ic and in some cases carcinogen

Carcinogen

A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...

ic. Testing for the presence of these dyes, and other additive

Additive

Additive may refer to:* Additive function, a function that preserves the addition operation* Additive inverse, an arithmetic concept* Additive category, a preadditive category with finite biproducts...

s can be done at many commercial laboratories.

Certification to the Oeko-tex standard

Oeko-tex standard

Oeko-Tex Standard 100 or Öko-Tex Standard 100 is an international testing and certification system for textiles, limiting the use of certain chemicals...

may also be applied for. This tests the component for over 100 different chemicals and certifies the component according to human ecological safety.