Allergic reaction after Diphenhydramine in dogs

The FDA has received 1,061 reports of allergic reaction in dogs after Diphenhydramine. That is 22% of all reports for this medicine, compared with 2.3% across reports for all dog medicines, so it is reported unusually often with this medicine.

1,061Reports

71%Marked serious

35%Recovered

9.9%Died or euthanised

Same dayTypical onset

How soon it started

Same day

756 76%

1–2 days

78 7.8%

3–7 days

43 4.3%

1–4 weeks

46 4.6%

Over a month

72 7.2%

How the animals did

Recovered

367 35%

Recovered with lasting effects

2 0.2%

Still unwell when reported

509 48%

Died

69 6.5%

Euthanised

36 3.4%

Not known

78 7.4%

Problems reported at the same time

602 57%

427 40%

290 27%

250 24%

199 19%

199 19%

172 16%

155 15%

Age of the animals

Under 1 year

108

1–3 years

496

4–7 years

260

8–11 years

144

12+ years

About this medicine

Type: medicine.

Questions owners ask

Can Diphenhydramine cause allergic reaction in dogs?: 1,061 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 the same day 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).

Allergic reaction with similar medicines

Allergic reaction after Melarsomine (Immiticide) 1,008 reports · 4.4% of its reports
Allergic reaction after Polysulfated Glycosaminoglycan 187 reports · 3.4% of its reports
Allergic reaction after Butorphanol 235 reports · 5.3% of its reports
Allergic reaction after Cefpodoxime 152 reports · 3.7% of its reports
Allergic reaction after Tramadol 74 reports · 2.0% of its reports
Allergic reaction after Florfenicol + Mometasone + Terbinafine 110 reports · 3.1% of its reports
Allergic reaction after Desoxycorticosterone Pivalate 172 reports · 5.2% of its reports
Allergic reaction after Propofol 196 reports · 6.4% of its reports
Allergic reaction after Isoflurane 137 reports · 5.0% of its reports
Allergic reaction after Cephalexin 77 reports · 2.9% of its reports

All reported side effects of Diphenhydramine in dogs · Medicines most reported with allergic reaction