http://www.soilassociation.org/whatisorganic/organictextiles/organicwool
Soil Association : Organic wool

Organic wool

Sheep are a natural resource in the UK, which has over 60 breeds. Organic wool comes from farms that put the sheep and the environment first. So as well as being a natural, renewable, biodegradable and durable fibre, when you buy organic wool you are also supporting more sustainable farming practice.

Organic wool has the following benefits:

It supports better animal welfare. Organic sheep are reared, fed, sheltered and transported with consideration for their wellbeing. Cruel practices are prohibited and animal stress is minimised. Organic farmers take a preventative approach to disease, so animals are not routinely treated with antibiotics, wormers or pesticides. Organic animals are reared on organic feed and grazed on organic land, and are free to pursue their natural behaviour with plenty of space outside and a free range life.

It doesn't use harmful manufacturing chemicals. Our standards ensure that the chemicals used in processing textiles meet strict requirements on toxicity and biodegreadability, and textile manufactures must also have a waste water treatment plant and a sound environmental policy. In contrast non-organic manufacture uses tens of thousands of acutely toxic chemicals, including heavy metals, formaldeyde and aromatic solvent, many of which are classified as hazardous by the World Health Organisation (WHO) and have been associated with cancer, birth defects and hormonal and reproductive effects in wildlife and humans. 

The end garments are residue free. By prohibiting and restricting harmful chemicals in organic textile production and processing, final products don’t contain allergenic, carcinogenic or toxic chemical residues from them. Tests on conventional clothing have revealed traces of pesticides, fire retardants, formaldehyde and toxic dyestuffs. These residues can be inhaled or absorbed through the skin and may cause allergies, skin rashes or respiratory problems. Babies are particularly vulnerable as their skin is much thinner than adults.