From the FTC clothes captioning link above.
Exceptions to the fiber disclosure requirement
Some parts of a textile or wool product don’t have to be counted for labeling purposes even if they are made of a fibrous material. These include trim, linings (unless used for warmth), small amounts of ornamentation and the threads that hold the garment together, although the label may need to disclose that the stated fiber content is exclusive of decoration or ornamentation.
Trimmings
Various forms of trim incorporated into clothing and other textiles are excluded from the labeling requirements.16 Trim includes collars, cuffs, braiding, waist or wrist bands, rick-rack, tape, belting, binding, labels, leg bands, gussets, gores, welts, FINDINGS, and superimposed hosiery garters.
Findings include:
ELASTOC materials and threads added to a garment in minor proportion for structural purposes; and
elastic material that is part of the basic fabric from which a product is made, if the elastic doesn’t exceed 20% of the surface area. In this case, the required fiber content information should be followed by the statement “exclusive of elastic.”
Other trimmings exempt from labeling requirements are:
decorative trim applied by embroidery, overlay, applique or attachment
decorative patterns or designs that are an integral part of the fabric
as long as the decoration does not exceed 15% of the surface area of the item. If no representation is made about the fiber content of the decoration, the fiber content disclosure should be followed by the statement “exclusive of decoration.”
