Hair loss after Spinosad (Comfortis) in dogs

503 reports to the FDA describe hair loss in dogs given Spinosad. That is 0.9% of all reports for this medicine, compared with 1.0% across reports for all dog medicines.

503Reports

15%Marked serious

27%Recovered

2.2%Died or euthanised

13 daysTypical onset

How soon it started

Same day

69 30%

1–2 days

24 10%

3–7 days

14 6.1%

1–4 weeks

41 18%

Over a month

81 35%

How the animals did

Recovered

33 6.6%

Recovered with lasting effects

104 21%

Still unwell when reported

63 13%

Died

5 1.0%

Euthanised

6 1.2%

Not known

292 58%

Problems reported at the same time

Itching

209 42%

Skin rash or irritation

97 19%

96 19%

50 9.9%

40 8.0%

39 7.8%

31 6.2%

29 5.8%

Age of the animals

Under 1 year

1–3 years

128

4–7 years

137

8–11 years

102

12+ years

About this medicine

Spinosad kills fleas; monthly chewable.

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

Questions owners ask

Can Spinosad cause hair loss in dogs?: 503 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 13 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 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 Flumethrin + Imidacloprid (Seresto) 135 reports · 5.9% 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 Spinosad in dogs · Medicines most reported with hair loss