Oeko-Tex Standard 100 is an international testing and certification system for textiles. It was developed in 1992 with the aim of limiting the use of certain chemicals. The Oek-Tex Standard 100 is concerned with the human ecology and addresses concerns about formaldehyde and other residues that remain in most manufactured clothing. However, it follows that manufacture without the use of harmful toxins is also good for the environment.
Responsibility for the Oeko-Tex Standard 100 is shared between the 17 test institutes which make up the International Oeko-Tex Association, which has branch offices in more than 40 countries worldwide. The criteria catalogue which forms the basis for the tests for harmful substances is based on the latest scientific findings and is continually updated; the human ecological safety of the textiles tested are more far-reaching every year. The test criteria and the related test methods are standardized on an international level and are widely included as guidance in terms and conditions of purchase and delivery right through to the retail sector. With a total of over 51,000 certificates issued for millions of different individual products, and over 6,500 companies involved worldwide, the Oeko-Tex Standard 100 has become the best known and most successful label for textiles tested for harmful substances.
The Oeko-Tex label is a recognized benchmark for the consumer and also serves as an additional quality assurance tool for the manufacturer. The concept has become established as a safety standard throughout the textile manufacturing chain and enables checks to be made for any harmful substances at each stage in the production process. The test samples are tested by the independent Oeko-Tex institutes for their pH-value, formaldehyde content, the presence of pesticides, extract-able heavy metals, chlorinated organic carriers and preservatives such as pentachlorophenol and tetrachlorophenol. The tests also include checks for any MAC amines in azo dyestuffs and allergy-inducing dyestuffs.
Allergy-inducing dyestuffs are particularly relevant to textiles. Textile dyes, which can be divided into several types (i.e. disperse, reactive, acid and direct) are the main causes of textile contact dermatitis. There has been an increasing frequency of contact dermatitis to clothing, in part undoubtedly to the greater awareness of this condition. Although dyes in clothing may be allergenic, there is a difference between a patch test, where the dye is placed directly on the skin, and a dyed textile where the dye will not transfer as easily to the skin; however, excess dye on a fabric may be readily available to the skin. As well as this, the prevalence of sensitization to dyes is quite high among the allergic population. A study in 2003 indicated that 12.3% of those patch tested were allergic to a dye and/or resin allergen; the highest incidence of sensitization from the dye group allergens was due to Disperse Blue 124, 106 and 85; these Disperse dyes have also been shown to induce purpuric contact dermatitis. Although the presence of allergenic or harmful dyes is of obvious relevance to clothing, it also has relevance to children's stuffed toys where the fabric may often be in direct contact with the skin. In the EU some steps have been taken towards testing for these types of dyes in toys, embodied in EN71-9,  although at present this is a voluntary standard, unlike parts 1–3 of the same standard.
The use of flame retardant and biocidic finishes is also prohibited in the clothing sector. The certificates issued are distributed or allocated in line with the international guidelines and specifications of the Oeko-Tex Test Association.
The test costs depend on which of the four Oeko-Tex product classes the product falls under
The greater the contact with the skin, the more stringent the requirements.
If all components of a textile comply with the requirements of the Oeko-Tex criteria catalogue without exception, the textile manufacturer receives certification and is entitled to use the Oeko-Tex label to mark the products in the shops. The Oeko-Tex certificate is issued for a period of one year and can be extended subject to further successful testing. In order to ensure ongoing compliance with the test criteria, the authorised Oeko-Tex Institutes carry out control tests every year on a minimum of 15% of all certificates issued on Oeko-Tex products available in the shops.