Formaldehyde provides greater durability and effectiveness in hair straightening processes, and with these purposes, became commonly used irregularly. With Brazilian law, RDC n° 79, 2000 (Anvisa), the use of formaldehyde in cosmetics is allowed in maximum 0.2 % concentration, exclusively for conservation. Because it is a substance that can cause small irritation to carcinogenesis, the aim of this study was to check whether the main hair straighteners used in Linhares, ES-Brazil are meeting the specifications required by applicable law. Ten samples of different brands were collected and based on the Guide to Quality Control of Cosmetic Products of ANVISA realized qualitative analysis through identification with the Schiff reagent and dosing done by reaction with acetylacetone. Of the ten products tested, all showed formaldehyde and 80% had levels above permitted. These results indicate the need for strict and constant control of hair straighteners marketed and awareness strategies about the risks of use of formaldehyde.