Hair loss after Flumethrin + Imidacloprid (Seresto) in dogs

The FDA has received 135 reports of hair loss in dogs after Flumethrin + Imidacloprid. That is 5.9% of all reports for this medicine, compared with 1.0% across reports for all dog medicines, so it is reported unusually often with this medicine.

135Reports

39%Marked serious

21%Recovered

1.5%Died or euthanised

46 daysTypical onset

How soon it started

Same day

8 7.8%

1–2 days

9 8.8%

3–7 days

6 5.9%

1–4 weeks

18 18%

Over a month

61 60%

How the animals did

Recovered

28 21%

Recovered with lasting effects

1 0.7%

Still unwell when reported

45 33%

Died

2 1.5%

Not known

59 44%

Problems reported at the same time

Itching

77 57%

Application site reaction

44 33%

Didn't stop fleas

43 32%

Skin redness

31 23%

Skin rash or irritation

24 18%

Lethargy

12 8.9%

Loss of appetite

11 8.1%

Behaviour change

10 7.4%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Imidacloprid kills fleas (spot-on or collar).

Products with this combination include Seresto. The FDA hides brand names in its public data, so these reports cover every product with the same active ingredients.

Questions owners ask

Can Flumethrin + Imidacloprid cause hair loss in dogs?: 135 reports link the two, but a report alone does not prove the medicine was the cause: other illnesses, other medicines or coincidence can be involved. Your vet can judge it for your animal.
How soon after a dose was it reported?: In half of the reports with dates, it started within 46 days of the first dose.
What should I do?: Don't give another dose until you've spoken to your vet, and keep the packaging so you can tell them the product and dose. Your vet can also report it to the FDA (or you can, through the manufacturer or FDA form 1932a).

Hair loss with similar medicines

Hair loss after Spinosad (Comfortis) 503 reports · 0.9% of its reports
Hair loss after Lufenuron + Milbemycin Oxime (Sentinel) 227 reports · 0.9% of its reports
Hair loss after Imidacloprid + Moxidectin (Advantage Multi) 452 reports · 3.4% of its reports
Hair loss after Nitenpyram (Capstar) 195 reports · 1.8% of its reports
Hair loss after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 46 reports · 0.5% of its reports
Hair loss after Fipronil + S-methoprene (Frontline Plus) 113 reports · 3.8% of its reports
Hair loss after Imidacloprid 43 reports · 2.3% of its reports
Hair loss after Fipronil 22 reports · 1.6% of its reports
Hair loss after Lufenuron 45 reports · 4.4% of its reports
Hair loss after Imidacloprid + Permethrin + Pyriproxyfen 33 reports · 4.5% of its reports

All reported side effects of Flumethrin + Imidacloprid in dogs · Medicines most reported with hair loss