Peru balsams (PB) are ingredients of human and veterinarian pharmaceuticals, but they are also considered to bear a risk to provoke allergenic reactions. Although observations after the application of 25 % PB in petrolatum exist in dogs, chemically defined undiluted balsams have not been investigated so far. Therefore, in the present study the dermatological compatibility of chemically defined, undiluted PB of different qualities was investigated for the first time. Six Peru balsams of different chemically defined quality and origin and their main compounds, nerolidol and benzyl benzoate, were tested in ten dogs (Beagles) by means of a closed patch test in comparison to a positive (sodium lauryl sulphate) and a negative control (water) in order to evaluate their irritating and allergic potential. Erythema and oedema were assessed using two different evaluation methods. All tested PB and nerolidol were evaluated as negligible irritant showing a primary dermal irritation index (PDII) between 0.025 and 0.350, whereas the positive control was assessed as slightly irritant with a PDII of 1.075. Most of the skin reactions arose and disappeared within the first 24 hours and did not extend beyond the testing site. These kinds of reactions are more characteristic of irritations than of allergies. The risk of contact dermatitis in dogs is considered to be very low when pharmaceuticals or care products containing PB are applied.