I threw the box away: is it still worth recording?

Yes, and it is still worth reporting. The batch number makes a report stronger because it lets independent cases be linked, but its absence does not make the rest useless: the product name, the timings, the signs and the outcome remain valid information. If you still have the blister, the bottle or even just the pharmacy receipt, photograph them: sometimes the batch appears on one of those rather than on the outer box.

My animal vomited once and was then fine: should I record it?

Yes, and it costs thirty seconds. An isolated mild episode stays an isolated mild episode, but if it recurs at the next administration your note becomes the second point in a series, and two points draw a line that one cannot. Recording mild events is also the only way to notice that one specific product always causes trouble, something that never emerges from memory alone.

How do I know whether it is the illness or the drug?

Often you do not, and it is not yours to decide. The three data points that help most are the interval between administration and the appearance of the signs, how the signs behave after a withdrawal decided by the vet, and the list of everything else the animal was receiving. Collect those three and the distinction is made by whoever holds the full clinical picture. The trap to avoid is waiting until you are sure before writing anything down, because the data disappears meanwhile.

If I report it, will the product be withdrawn?

Almost never on a single report, and that is not the purpose. Reports feed a surveillance system looking for recurring patterns: an unusual number of cases on one batch, an effect not described in the product information, a species in which the product turns out to be less well tolerated. Possible consequences range from an update to the product information through to more serious measures, but they come from accumulation rather than from one case.

The reaction involves a food rather than a medicine: does the same apply?

The recording method is identical and just as useful: product, batch, dates, signs, outcome and what else the animal was eating. What changes is the reporting channel, because foods and supplements follow a different chain from veterinary medicines. Ask your vet where a report should go in your country, and in the meantime keep the packaging and a portion of the product in its original container.

Health management25 minLevel: IntermediateUpdated on August 5, 2026

Keeping a record of adverse reactions

What counts as an adverse reaction, what to note in the first minutes, how it is told apart from illness and who the report actually goes to.

Audience: Pet owners, Veterinarians
Species: Dog, Cat, Rabbit
Scope: Valid everywhere, European Union

What you need before you start

La confezione del prodotto sospetto, con numero di lotto e data di scadenza ancora leggibili
L'elenco di tutto ciò che l'animale ha ricevuto nelle due settimane precedenti, farmaci e non
L'orario esatto dell'ultima somministrazione prima della comparsa dei segni
Un telefono per fotografare o filmare quello che stai osservando

When an animal reacts badly to something, the reaction is brief and the memory of it is briefer still. Within two days what remains is the impression that the vomiting started after the tablet, but not the time, not the batch number, not what it had eaten that morning. Yet those are exactly the details that separate an adverse reaction from a coincidence, and that allow the same substance to be avoided for the rest of the animal's life rather than being given again in three years by a clinic that never knew. This guide sets out what counts as an adverse reaction, what to note in the first minutes, how the link between substance and sign is reasoned about, where to record it so that it stays readable, and who to report it to.

What counts as an adverse reaction

The definition is wider than most people assume, and narrowing it is why most reactions are never recorded or reported. The sign does not have to be severe, the link does not have to be certain, and it does not even have to involve the animal.

Any unintended effect appearing after a product was given, including mild and transient ones.
Lack of efficacy: the product was used as intended and did not work. It is an adverse reaction in full and it is reported far too rarely.
Reactions in the person handling the product, for example on the skin after applying a spot on parasite treatment.
Effects appearing in an animal that was not the intended recipient, for example the cat that rubbed against the freshly treated dog.
Effects from foods, supplements and grooming products, not only from medicines.
Suspicion of a problem with the product itself: abnormal appearance, different smell, intact packaging with contents that do not match.

What to do and note in the first minutes

Deal with the animal first
If there is breathing difficulty, facial swelling, collapse or neurological signs, call the clinic and go. Documentation can be recovered later; the animal cannot.
Keep the packaging, do not throw it away
The batch number and expiry date live there and cannot be reconstructed anywhere else. If you have already binned the box, photograph whatever is left, including the blister or the bottle.
Note the exact time of administration and of the first sign
The interval between the two is the single most informative item in the whole report. A reaction at twenty minutes and one at three days point to completely different mechanisms.
Film what you are seeing
Swelling, tremors, difficulty walking, intense itching and altered breathing are described badly and filmed well. Shoot in landscape and include the whole animal.
Write the full list of everything given
All medication, but also supplements, new foods, treats, grooming products and environmental parasite treatments used in the house over the previous fortnight.
Note the current weight and how it was given
Many amounts depend on weight, and the route changes absorption: fasted or with food, on the skin or by mouth, whole dose or split.
Call the vet before stopping anything
For some treatments abrupt withdrawal is more dangerous than the reaction. Stopping should be decided by the prescriber, except with severe signs, in which case you call while heading to the clinic.
Write everything up the same day
By the next day the timings are already gone. Transcribe while the memory is fresh, even messily: tidying up is possible, reconstructing is not.

The twelve items that make a report usable

A generic description helps nobody. These are the items that make the same observation usable by a vet, by a surveillance system and by you in two years' time.

Minimum content of an adverse reaction record and why each item is needed.
Item	Why it is needed
Product name and active ingredient	Different products can contain the same molecule
Batch number	Allows independent reports to be linked to the same batch
Expiry date	Separates a product problem from use beyond the expiry date
Date and time of administration	Half the timing data, without which the interval does not exist
Date and time of the first sign	The other half: the interval points to the mechanism
Route and manner of administration	Skin, mouth, injection, fasted or with food all change absorption
The animal's weight at the time	Many amounts depend on weight
Description of the signs in everyday words	Vague terms such as it was unwell cannot be classified
Duration and course of the signs	Separates a single episode from a persistent reaction
What was done and with what effect	Withdrawal and the response to it are part of the reasoning about the link
Everything else given in the previous fortnight	Without that list every hypothesis stays half finished
Final outcome and its date	Resolved, resolved with sequelae, ongoing or not resolved

Telling a reaction from an illness

The reasoning about the link uses a few explicit criteria, and it is worth knowing them because they tell you which data to collect. They are not there for you to conclude on your own; they are there to make your description assessable.

The criteria used to judge the link and what to observe for each.
Criterion	What to observe
Time sequence	How long passed between administration and the first sign
Plausibility	Whether that kind of effect is already known for that class of product
Response to withdrawal	Whether the signs improved after stopping, and how quickly
Response to rechallenge	Whether they returned when the product was given again, which must never be provoked deliberately
Alternative explanations	Ongoing illness, other products, diet changes, environmental events
Repeatability in other animals	Whether other household animals treated at the same time showed anything

Where to record it so it stays readable

An adverse reaction only counts if somebody else finds it before repeating the exposure. In practice that means writing it in three different places, because each one is consulted at a different moment.

In the animal's allergies and conditions tab, which is the place people look before prescribing anything new.
In the record of the treatment involved, in the field for unwanted effects, so the information stays attached to the product.
In the health diary, as a dated entry with the full description of the episode and a pointer to the photographs.
In the document vault, uploading a photograph of the packaging with a legible batch number and any report from the visit.
On the paper health record book, in a handwritten line, because that is the document that travels with the animal without a battery.
In the public tag message only if the reaction is serious enough to make an administration in your absence dangerous, and without naming any drug.

The medicines page includes a panel that queries the public United States veterinary database of adverse event reports. Given an active ingredient and a species among dog, cat, horse, rabbit and bird, it returns the most reported reactions with the number of reports and their share of the total, along with the list of molecules that appear most often in the same reports.

Reporting, and what happens next

Recording at home protects your animal. Reporting protects everybody else's, and it is the only way a batch problem or a rare effect ever surfaces: surveillance systems work by accumulating individual cases, so a report that looks irrelevant on its own may be the one that completes a picture.

Ask your vet who submits the report in your country and on which form: procedures differ from one state to another.
In many countries a report can come from the vet, from the product's authorisation holder or directly from the owner.
Report even when the link is uncertain: judging the link is not the reporter's job.
Report lack of efficacy too, which is the most underrated category of all.
Keep the packaging until you are told it is no longer needed: in some cases the batch is requested for checks.
Ask for the reaction to be written into the clinic's own record, not just yours, so it survives a change of device.

After reporting, the most useful thing you can do is also the simplest: say out loud that the animal had that reaction, every time somebody is about to give it something. At the boarding kennel, at the groomer, at an out of hours clinic and to whoever looks after it while you are away. A well kept record is for you; a sentence said at the right moment is what prevents the second exposure.

Frequently asked questions

I threw the box away: is it still worth recording?: Yes, and it is still worth reporting. The batch number makes a report stronger because it lets independent cases be linked, but its absence does not make the rest useless: the product name, the timings, the signs and the outcome remain valid information. If you still have the blister, the bottle or even just the pharmacy receipt, photograph them: sometimes the batch appears on one of those rather than on the outer box.
My animal vomited once and was then fine: should I record it?: Yes, and it costs thirty seconds. An isolated mild episode stays an isolated mild episode, but if it recurs at the next administration your note becomes the second point in a series, and two points draw a line that one cannot. Recording mild events is also the only way to notice that one specific product always causes trouble, something that never emerges from memory alone.
How do I know whether it is the illness or the drug?: Often you do not, and it is not yours to decide. The three data points that help most are the interval between administration and the appearance of the signs, how the signs behave after a withdrawal decided by the vet, and the list of everything else the animal was receiving. Collect those three and the distinction is made by whoever holds the full clinical picture. The trap to avoid is waiting until you are sure before writing anything down, because the data disappears meanwhile.
If I report it, will the product be withdrawn?: Almost never on a single report, and that is not the purpose. Reports feed a surveillance system looking for recurring patterns: an unusual number of cases on one batch, an effect not described in the product information, a species in which the product turns out to be less well tolerated. Possible consequences range from an update to the product information through to more serious measures, but they come from accumulation rather than from one case.
The reaction involves a food rather than a medicine: does the same apply?: The recording method is identical and just as useful: product, batch, dates, signs, outcome and what else the animal was eating. What changes is the reporting channel, because foods and supplements follow a different chain from veterinary medicines. Ask your vet where a report should go in your country, and in the meantime keep the packaging and a portion of the product in its original container.

What to do next

Keep the packaging with the batch number, note the time of administration and of the first sign, film what you see and write everything up the same day. Record the reaction in the allergies tab, in the treatment involved and in the health diary, and upload a photograph of the packaging to the document vault. Then ask your vet who submits reports in your country, report even when the link is uncertain and even when the product simply did not work, and say it out loud to anybody about to give your animal anything.