They ARE bad, it's not just that they aggravate curly hair:
Sodium Lauryl Sulphate (SLS) and Sodium Laureth Sulphate (SLES).
These are found in shampoos, hair conditioners, toothpastes, body washes etc. They are strong detergents, which can cause irritation and permanent damage to the eyes (especially in children), skin rashes, hair loss, flaking skin and mouth ulceration.
When combined with other ingredients, they can form nitrosamines, which are carcinogenic and can easily pass through the skin into the bloodstream, accumulating in the heart, lungs, liver and brain.
See more here: www.healthychoices.co.uk/sls.html
Propylene Glycol (PG)
Material Safety Data Sheets warn users to avoid skin contact with this substance, and protective clothing should be worn at all times. It is the cosmetic form of mineral oil found in automatic brake fluid, hydraulic fluid and industrial antifreeze, yet is also found in make-up, hair and skin care products, deodorants, and aftershave.
The related agent, Polyethylene Glycol (PEG) that is found mainly in skin cleansers is a caustic used in industry to dissolve grease.
Both of these are strong skin irritants and can cause contact dermatitis, liver abnormalities and kidney damage.
It is the most common moisture-carrying vehicle, other than water, in cosmetics. It has better permeation through the skin than glycerin and is less expensive; although it has been linked to more sensitivity reaction.
See more here: www.healthychoices.co.uk/pg.html
Diethanolamine (DEA); Triethanolamine (TEA); Monoethanolamine (MEA)
These chemicals are found in children?s bubble baths. When combined with nitrosamines, these substances can become carcinogenic. They are able to pass directly into the blood stream and, in studies, have been found to induce cancer of the liver and kidneys in mice.
Although outlawed in some countries, DEA, TEA and MEA are still widely available in the UK and Ireland.
See more here: www.healthychoices.co.uk/dea.html.
HTH! :)