Concerns have been raised this month about the safety of certain dog chew products. The chews have been manufactured by the China-based companies ‘Barkoo’ and ‘Chrisco’. Dogs have become unwell after being given the chews, experiencing a collection of distressing symptoms that have been referred to as ‘werewolf syndrome.’ The Food Standards Agency (FSA) has issued a warning to dog owners in the UK, asking them not to offer the chews to their dog because of the health risk.

What is the health risk?

The European Union (EU) first raised concerns after dogs started showing some worrying behavioural changes after eating the chews. These included panic attacks, aggression, spasms and epileptic fits. It’s uncertain as to how many dogs in China and Europe have been affected, but in some cases, dogs are reported to have died. 

The FSA has been working closely with authorities in affected EU countries to learn more about the issue. No direct risk to human health has as yet been identified. 

The cluster of symptoms dogs have experienced after eating the chews has become known as ‘werewolf syndrome’. It’s still too soon to know exactly what toxin or ingredient is causing the problem, but the chews seem to affect the dog’s nervous system. The behaviour shown by the affected dogs has clearly been deeply distressing for owners to witness. 

The FSA has said that there’s been “no confirmed distribution of the chews to the UK” so it’s unlikely that dog owners here will find the chews in pet shops. So far, there have been no confirmed cases here either. However, it is possible that dog owners in the UK could purchase these chews through online retailers. That’s why the FSA has issued its warning for owners about the risks posed by these products.

Which products do I need to look out for?

The affected products include:

Barkoo kaustange natur 29 cm

  • Packaging: bags of 570 grams (with 3 chewing bones)
  • Code on packaging: 1148655 MHD 04.2027 3200PF027
  • Barcode: 4260077047292

Barkoo kauknochen, geknotet natur 11cm

  • Packaging: bags of 150 grams (with 3 chewing bones)
  • Code on packaging: 1148592 MHD 07.2027 3200PF027
  • Barcode: 4260077046875 

Barkoo Kauknochen geknotet 24cm

  • Packaging: bags of 150 grams (with 3 chewing bones)
  • Barcode: 4260077046899
  • Code on packaging: 1148657 MHD05.2027 3200PF027

Barkoo Kauknochen geknotet mit Spirulina 12cm

  • Packaging: bags of 180 grams (with 3 chewing bones)
  • Barcode: 4260077047261
  • Code on packaging: 1148654 MHD 06.2027 3200PF027

Chrisco Tyggeruller med kylling, 10 stk (No image available)

  • Item number: 12457
  • EAN code: 5764630124578
  • Use by dates: all dates

Chrisco Tyggeruller med kylling & kyllingelever, 100g 

  • Product no. 12324
  • EAN code: 5764630123243
  • Use by dates: 01/12/2025; 05-01-2026; 15-03-2026; 18-03-2026; 15-04-2026; 20-04-2026; 01-06-2026; 15-07-2026

Chrisco Tyggeruller 18 stk. – hvide 

  • Product no. 12468
  • EAN code: 5764630124684
  • Use by dates: 05/01/2027; 26-02-2027; 15-03-2027; 18-03-2027; 24-03-202

Chrisco Massive politistave, 2.stk. – brune       

  • Product no. 12541
  • EAN code: 5764630125414
  • Use by dates: 26/02/2027; 15-04-2027

Chrisco Massive politistave, 2stk. – hvide      

  • Product no. 12542
  • EAN code: 5764630125421
  • Use by dates: 05/01/2027; 20-04-2027; 01-06-2027

Chrisco Tyggerulle m. kylling & kyllingelever, 1stk  

  • Product no. 12624
  • EAN code: 5764630126244
  • Use by dates: 01/12/2025; 05-01-2026; 15-03-2026; 18-08-2026

What is the advice for dog owners?

Avoid any of the products listed if you are purchasing dog chews online. So far, these products have not been sent to the UK through commercial pet shops and retailers, but it is possible that you may be able to purchase them online. 

Many of these products have long shelf lives. Check your cupboards as they may have been bought several months ago. 

If you have fed the affected chews to your dog, stop doing so immediately. Look out for any signs that your dog may be unwell. If your dog is acting out of sorts, you should speak to your vet straight away. If you can, it’s a good idea to provide detailed information to the vet about the foods and treats your dog has been fed.

What advice has been issued for vets?

Vets have been informed about the chews, and where dogs have eaten them, they need to look out for symptoms such as: 

  • sudden behavioural changes like howling, crying and aggression
  • epileptic-type seizures

If vets suspect cases associated with dog chews, they can report them through the Food Standards Agency to foodincidents@food.gov.uk adding reference number I-009-004.

Are dog chews generally safe for dogs?

The FSA is asking owners to avoid the Barkoo and Chrisco dog chew products listed above. 

But most dogs love to chew, and there are safe chew toy options available. 

Make sure you choose wisely, as chew toys in general can cause harm. Every day, vets see chew-toy related problems like cracked teeth, and gut blockages that may even lead to death. That’s why it’s important to select a safe chew toy for your dog, and to supervise them while they have it.

Things to look out for when choosing a chew toy: 

  • If the chew is harder than the teeth, it might cause a tooth injury.
  • Is it possible for your dog to bite off chunks that are indigestible? If so, this could cause a dangerous gut blockage if they are swallowed.
  • Can chunks get stuck in the windpipe or oesophagus and lead to choking?

For the reasons stated above, it might be best to avoid bones, antlers, horns and rawhide (Why Is Rawhide Bad for Dogs? – Vet Help Direct). Collagen chews, dried fish skins, and vegetables like carrots can be a safer alternative. Non-edible chews made of rubber, plastic, fabric or other synthetic materials can also be offered to your dog, or you might want to browse the recommended products listed by the Veterinary Oral Health Council. It’s important to only give your dog a chew when you are around to supervise, just in case.