Cresole

Cresols (also known as hydroxytoluenes or methylphenols) form a group of aromatic compounds derived from both phenol and toluene. Their structure consists of a benzene ring with a hydroxy (-OH) and a methyl group (-CH3) as substituents. The different arrangement of the substituents results in 3 isomers, m-cresol, o-cresol, p-cresol with the common molecular formula C7H8O.

The various cresols and their mixtures of isomers act as bactericides, insecticides and fungicides (see below preservatives). They are therefore often used as components of disinfectants, body care products, hair care products, hair dyes and mouth rinses (see also p-chloro-m-cresol).

m-cresol is used as a preservative in various products. Insulin products.

In technical products, cresols are used as a starting product for dyes, synthetic resins and medicines. They are also used for the preservation of e.g. glue, adhesives and inks.

Allergological/toxicological assessment: In principle, however, based on the available data, cresols are to be classified as safe and well tolerated by the skin as ingredients of cosmetics and skin care products up to a concentration of 0.5 %.

At higher concentrations, cresols, like phenols, have a protein precipitating (corrosive) effect depending on the concentration. They cause acute damage on contact with skin and mucous membranes. Toxic irritations, also mucous erosions or ulcers are to be expected in case of inhalation exposure. Thus, 2% p-chloro-m-cresol In epicutaneous tests can cause irritative-toxic reactions.

Signs of chronic damage caused by increased phenol or cresol concentrations in indoor environments include coughing, headache, nausea, loss of appetite, drowsiness and insomnia (see also ecosyndrome).

Allergological evaluation: There is little evidence for type IV sensitization of cresols, despite their long-standing use. Isolated contact allergic reactions have been observed with hair dye products containing cresol (especially o-cresol) (Bruze M et al 2002). Local, but also severe systemic, side effects have been described with the injection of m-cresol-containing insulins (Rajpar SF et al 2006).

Vitiligo: There is evidence of an (occupational) induction of vitiligo by p-tert-butylphenol. For butyl-cresol (butylated hydroxytoluene) this side effect is not confirmed. (Broding HC et al 2011).

Carcinogenicity: Phenols and cresols are considered to be carcinogenic. They pose a cancer risk depending on the concentration.

1. Brocca A et al (2013) Cytotoxic effects of p-cresol in renal epithelial tubular cells. Blood Purif 36(3-4):219-225.
2. Broding HC et al (2011) Induction of occupational leucoderma and vitiligo. Can butylated hydroxytoluene induce vitiligo similarly to p-tert-butylphenol? Dermatologist 62:209-214.
3. Bruze M et al (2002) Contact allergy to o-cresol, a sensitizer in phenol-formaldehyde resin. Am J Contact Dermat 13: 198-200
4. Cresol, safety data sheet.
5. Rajpar SF et al (2006) Severe adverse cutaneous reaction to insulin due to cresol sensitivity. Contact dermatitis 55:119-120.