Shampoo is a hair care product designed to clean the skin and hair of the scalp. Among the ingredients that go into the making of a shampoo are detergents, conditioners, thickeners, sequestering agents, pH adjusters, preservatives, and active ingredients such as anti-dandruff agents. The purpose of this study was to identify the composition of 140 shampoos available in pharmacies, in stores of a mass-market chain, or from mail-order retailers. Forty-one shampoos were advertised as "gentle", 12 as specially formulated for infants, 35 as anti-dandruff, and 52 without any particular claim. We analysed the cleansing base, preservatives, and anti-dandruff agents when relevant and identified the allergens regardless of whether or not they are listed under Regulation (EC) No. 1223/2009 as one of the 26 regulated substances. We discovered that unlike shampoos sold in stores of a mass-market chain and those available from mail-order retailers, those sold in pharmacies expose users to some of the 26 substances listed under Regulation (EC) No. 1223/2009. We also determined that baby shampoos sold in pharmacies are allergen-free. Regarding anti-dandruff formulations, the largest variety of active ingredients was found in shampoos sold in pharmacies. Overall, the most common active ingredients were olamines, zinc pyrithione, azoles, selenium disulphide, and plant extracts. Shampoos sold in pharmacies appear to contain fewer allergens listed under Regulation (EC) No. 1223/2009 compared to those sold elsewhere.