How do Brazilian keratin treatments really work?

Some sample ingredient lists

Simply Smooth ingredients: Water, Hydrolyzed Keratin, Propylene Glycol, Vanillin , Cetrimoniun Chloride, Hydrolyzed Collagen, Cetearyl Alcohol, Ceteareth-20, Amodimethicone, Cyclopentasiloxane, Dimethicone, Imidazolidinyl Urea, Fragrance , Yellow 5 (Ci 19140), Orange 5 (Ci 15510)

Liquid Keratin 30 Day Straight Smooth Strong & Long Treatment: Purified Water , Dimethicone, Dimethiconol , Sodium Cocoyl Amino Acids (Aspartic Acid, Glutamic Acid, Alanine, Glycine) ,Biformyl, Potassium Dimethicone Peg-7 Panthenyl Phosphate , Keratin, Sodium Laneth-40 Maleate / Styrene Sulfonate Copolymer, Phenoxyethanol , Ethylhexylglycerin Laureth 4 , Laureth-23 , Hydrolyzed Keratin

QOD Cosmetics QOD GOLD: Cetyl Alcohol (organic co-emulsifier), Cetrimonium Chloride (emulsifier, anti-bacterial), Lanolin (ultra pure medical grade, hypoallergenic), Dimethicone (organo-substituted skin protectant), Bio-Organic Hydrolyzed Keratin Complex, Polyquaternium 7 (positively charged, patented), Methylparaben (naturally occurring antimicrobial), Propylparaben (antimicrobial), Urea (water soluble), Bio-Organic Hydrolyzed Keratin Complex (patented), Fragrance (natural, tropical fruit essence), CL 77480 (Pure 24 Karat Gold, medical grade), Aqua (purified), Cyclopentasiloxane (organically bound silicon), Dimethiconol (skin protectant, non toxic alternative to ozone depleting chemicals).

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Tonya McKay

Tonya McKay Becker is a curly-haired polymer scientist and cosmetic chemist whose academic and industrial research experience have provided her with expertise in the fundamentals and applications of polymer science and colloid chemistry. She has long had a fascination with the structure-property relationships of the complex solutions used in hair and skin care products, and how they interact with and impact these remarkable biological substrates. Ever curious, Tonya has dedicated herself for more than a decade to honing her expertise on the science of curly hair, how it differs from straight hair, and how product ingredients used on curly hair affect its health and beauty. Her passion for sharing this knowledge with others has led to her current career of educating people from all backgrounds who share an interest in this exciting field.