First identify the claim
Hair describes a sample. Bioresonance describes a claimed approach to measurement. These terms are not interchangeable, and a study of a hair-based product does not automatically establish how every product works.
The UK Committee of Advertising Practice’s explanation of bioresonance advertising describes claims about biological frequencies. That explanation is useful for understanding the terminology; it is not veterinary evidence that a frequency-based method diagnoses a dog’s allergy.
One vendor’s sample pet report describes bioresonance while stating that it does not diagnose allergies. A change in label from allergy to intolerance does not, by itself, answer whether the reported classifications have been clinically validated.
What the animal studies found
Bernstein and colleagues studied a commercial hair-and-saliva analysis using samples from healthy animals and animals with atopic dermatitis and synthetic material. The evaluated test did not reliably distinguish the groups, and repeat results did not perform better than chance. The study included cats as well as dogs and a small number of animals.
A separate study by Coyner and Schick also found weak repeatability in the test it examined. These findings concern the products and submissions evaluated. They should not be rewritten as a head-to-head assessment of every kit now on sale.
Ask two different evidence questions
First, does a test produce consistent results when the same material is tested again? Second, does its result distinguish the clinical condition it claims to identify? Consistency alone would not establish clinical accuracy. An explanation of a mechanism, a list of items tested or an impressive-looking certificate would not answer both questions either.
Ask the provider for a published validation study of its exact method and intended use in dogs. Check the comparison used and whether the studied animals resemble the population the product is marketed to.
Accuracy concerns are not a measured injury rate
The cited studies assess test performance. They do not establish how often a kit causes injury, malnutrition or delayed diagnosis. Hair collection itself should not be described as dangerous on the basis of these findings.
The concern is reliance on a result that may not support the decision being made. Before changing food or care, discuss the complete report, your dog’s history and the evidence with your veterinarian. Read the testing overview for the distinction between food-reaction investigations and environmental-allergen testing.