Rawhide dog chews are made from the inner split layer of cattle hides — the dermis — processed industrially to create a white, odourless product. The processing sequence involves strong alkali (sodium hydroxide lime solution) to remove hair and fat, chromium-based or glutaraldehyde tanning to stabilise the hide, hydrogen peroxide or sodium hypochlorite bleaching for whitening, and chemical treatment to prevent microbial growth. Residues of processing chemicals remain in the finished product. Chromium VI (hexavalent chromium), introduced during tanning, is of particular concern — it is a confirmed human carcinogen via inhalation and a potent skin and mucosal sensitiser. When a dog chews rawhide, it salivates copiously and residual chemicals dissolve into the saliva, which then contacts human skin during handling and dog licking of human hands and faces.
Where it's found
Rawhide chews, bones, and sticks sold in pet shops, garden centres, and online (common brands include Good Boy, Carnivore Crisps, and unbranded imported products). Pressed rawhide items (twisted rolls, knotted bones) that have been formed under industrial pressure from processed hide. Rawhide-wrapped dental chew products. The bulk of UK rawhide products are manufactured in Asia (China and India particularly) where tanning regulation may differ from EU standards. Coloured rawhide products (red, green, and multicoloured chews) contain additional dyes whose safety in chewable pet products is not specifically regulated.
Routes of exposure
Pets are directly exposed via oral contact during chewing — chromium compounds in the rawhide dissolve in saliva and are ingested. Humans are exposed through handling the chew before giving it to the dog, through contact with the dog's saliva when the dog licks human hands and faces after chewing, and via hand-to-mouth transfer when preparing or touching rawhide products. Children who play near a chewing dog have elevated incidental exposure. The saliva-contact pathway means that regular cuddlers of rawhide-chewing dogs receive repeated low-level chromium and bleaching chemical exposure on facial skin.
Health concerns
Hexavalent chromium Cr(VI) is classified as a confirmed human carcinogen (IARC Group 1) — it is the compound responsible for the Hinkley, California groundwater contamination that was the subject of the Erin Brockovich case. Cr(VI) is a potent skin sensitiser and one of the leading causes of occupational allergic contact dermatitis (chrome allergy) in construction workers exposed to cement. In rawhide, Cr(VI) residues are present in a context where direct mucosal and skin contact occurs via saliva. Chrome allergy from rawhide handling has been reported in the dermatological literature. Formaldehyde (used as a preservative in some rawhide products) is a Group 1 carcinogen and skin sensitiser. Bleaching agents and alkali residues cause mucosal irritation.
Evidence
Chromium VI carcinogenicity (lung cancer via inhalation) is established (IARC Group 1). Cr(VI) skin and mucosal sensitisation causing allergic contact dermatitis is well established occupationally. Case reports of allergic contact dermatitis attributable to rawhide handling in dog owners have appeared in the dermatological literature. The specific cancer risk from rawhide-derived Cr(VI) via the saliva contact route at consumer doses has not been quantified epidemiologically. Residual Cr(VI) in rawhide products is documented by chemical analysis studies of retail products in European markets.
Who's most at risk
Children who handle rawhide chews and whose faces are licked by rawhide-chewing dogs — highest hand-to-mouth and skin contact rates. Individuals with existing chromium allergy from occupational cement or leather exposure. People who handle multiple rawhide products daily in retail or veterinary settings. Dogs themselves who ingest processing chemical residues over years of rawhide consumption.
Regulatory status
RegulationPet chews are regulated as animal feed in the UK under the Animal Feed (Hygiene, Sampling etc.) Regulations 2015. Contaminant limits for heavy metals including chromium apply in principle. However, specific Cr(VI) limits for pet chews are not set in UK or EU pet food legislation. Rawhide is exempted from some food contact material regulations that would otherwise apply. Consumer product safety regulations require rawhide products to be safe for their intended use, but enforcement testing is limited. EU REACH restricts Cr(VI) in leather articles intended for skin contact, but rawhide pet chews sit in a regulatory gap.
How to reduce your exposure
Choose Cr(VI)-free alternatives for dog dental health: natural, single-ingredient chews (dried tendons, rabbit ears, deer antler, natural fish skins) avoid the chemical tanning process entirely. Vegetable-based dental chews (VegaDent, Whimzees) are free of animal hide processing chemicals. If you use rawhide products, wash hands after handling and before food preparation or face contact. Discourage dogs from licking faces immediately after rawhide chewing sessions. Look for rawhide products that declare chromium-free tanning processes on labelling.
The nutrition connection
Hexavalent chromium Cr(VI) is a potent oxidant that depletes cellular antioxidant reserves — it is reduced intracellularly to Cr(III) in a process that generates reactive oxygen species and depletes glutathione. Adequate vitamin C status is particularly relevant: vitamin C in saliva and gastric mucosa can reduce Cr(VI) to the less toxic Cr(III) before it reaches cells, providing a front-line reduction reaction. Selenium (glutathione peroxidase cofactor) and vitamin E support cellular antioxidant capacity. Adequate protein intake ensures glutathione precursor availability. These nutritional factors are relevant both to the dog owner and potentially to the pet.