What is the controversy with the Seresto flea collar?

Understanding the Controversy Surrounding Seresto Flea Collars

The Seresto flea and tick collar has become a widely used method for controlling external parasites on pets, with over 70 million units sold worldwide. Although effective for many pet owners, Seresto has also faced significant controversy due to reports of adverse events and pet deaths.

Composition and Effectiveness

Seresto collars are designed to provide up to eight months of protection against fleas and ticks. They contain two active ingredients:

• Imidacloprid: a neonicotinoid targeting fleas
• Flumethrin: a pyrethroid that repels and kills ticks

The ingredients are embedded in a polymer matrix that gradually releases the chemicals over time. Veterinarians and studies indicate that the collar is generally effective when used appropriately, with pets remaining protected even after swimming or bathing (though frequent washing may reduce its efficacy).

The EPA Review and Safety Concerns

In 2021, the U.S. Environmental Protection Agency (EPA) began a thorough review of Seresto following a significant number of incident reports, including 1,400 pet deaths from 2016 to 2020. However, many reports lacked critical information. The EPA found that in most death cases:

• This was either due to mechanical failure (e.g., collar strangulation)
• Or related to pre-existing health issues

Only a small proportion of cases had a probable or definitive link to the collar.

Common Adverse Reactions

Reported non-lethal incidents ranged from mild to moderate symptoms:

• Skin irritation and redness
• Hair loss around the collar area
• Neurological symptoms like ataxia or convulsions

In many situations, symptoms subsided after collar removal. Reapplication often triggered recurrence.

EPA Mandates and Manufacturer Response

In light of safety concerns, the EPA required manufacturer Elanco Animal Health to:

• Enhance warning labels and provide clear guidance for symptom management
• Submit improved incident reporting and collect more detailed health data
• Evaluate and potentially redesign the collar’s release mechanism
• Maintain annual safety reporting and a five-year registration review

Elanco has stated that less than 0.2% of collars sold have yielded incident reports, and most involved mild effects. Their internal assessments found no direct association between the active ingredients and fatal outcomes.

The Risk of Counterfeit Products

Another issue exacerbating the controversy is the presence of counterfeit Seresto collars sold through online platforms. Many adverse reactions were linked to fake products, which often differ in formulation and safety. To mitigate this risk:

• Purchase only from veterinarians and authorized retailers
• Inspect packaging for authenticity indicators

When to Avoid Use

Caution is advised for certain pet populations:

• Pregnant or lactating animals
• Pets with a history of sensitivity to topical treatments

Consultation with a veterinarian is recommended in these cases, as studies on these groups are limited.

Veterinary Guidance and Monitoring

Veterinary experts continue to support year-round flea and tick control, noting that the risk of vector-borne diseases, such as Lyme disease, outweighs the rare possibility of side effects from treatments like Seresto. Still, pet owners should:

• Closely monitor their pet after collar application
• Remove the collar and consult a veterinarian if symptoms develop
• Follow all label instructions regarding fit and duration

Final Thoughts

While the controversy surrounding the Seresto collar is complex, much of the concern arises from a small subset of cases among millions of users. The product remains widely endorsed by veterinarians and is considered effective when used correctly. Awareness, proper monitoring, and purchasing through reliable channels can further reduce risks and ensure pet safety.