Chocolate has long been recognised as, and remains, a common cause of intoxication
in dogs accounting for 25 per cent of acute presentations for intoxication.1 2 Case
numbers in Europe and the UK have been reviewed, mostly based on reports to poisons
centres.3–6 Chocolate toxicity results from the methylxanthine theobromine present
in cocoa bean products, causing gastrointestinal (eg, vomiting), cardiovascular (eg,
tachycardia) and central nervous (eg, agitation and seizure) signs.7 Chocolate intoxication
is mostly seen in dogs6 8 and theobromine dose calculations based on the source of
chocolate are well documented7 9 and available online. 10 11 The current study reviews
cases of chocolate exposure presented to a large sentinel network of UK veterinary
practices between 2012 and 2017.
Electronic health records were collected from 229 UK veterinary practices (500 premises)
by the Small Animal Veterinary Surveillance Network (SAVSNET).12 Records included
the consultation time, species, breed, sex and clinical free text (narrative) in which
inadvertent personal identifying data contained in narratives had been redacted using
deidentification software (Newman). Narratives were screened using a regular expression13
to identify the presence of the word ‘chocolate’, including a range of misspellings
and contractions (eg, ‘choc’, ‘choclat’). Cases were tagged for study inclusion if
on reading they matched a definition of potential chocolate exposure whereby ingestion
triggered either specific treatment or a plan of monitoring for clinical signs of
theobromine toxicity.
Data were wrangled using the Pandas library14 in Python V.3.415 and analysed using
Stata V.12.16 Five unmatched controls were randomly selected for each case using animals
not identified by the initial screening for chocolate. To analyse risk periods, a
categorical variable was generated to indicate whether a consultation occurred from
one week before to two weeks after Christmas, Easter, Valentine’s Day or Halloween.
Univariable analysis of the effect of sex-neutering status, age category (0 to <4
years, 4 to <8 years, 8 years and over) and risk period was undertaken. Variables
that showed a significant effect were included in a multivariable logistic regression
model. The effect of breed was analysed using Fisher’s exact tests for each breed
separately (to accommodate small numbers of individuals involved) and interpreting
the P value following a Bonferroni adjustment.
In total, 1722 consultations referring to chocolate were identified from 2.7 million
narratives collected between November 2012 and May 2017 and of these 386 (22 per cent)
narratives from 375 individual animals were identified as matching the chocolate exposure
case definition. Where an animal appeared more than once, only the first consultation
was retained. Many cases (101, 26 per cent) presented within one hour of ingesting
chocolate and the majority (217, 56 per cent) presented within six hours. Vomiting
following ingestion was frequently noted (64 cases, 17 per cent), while neurological
signs (agitation, restlessness) were uncommon (12 cases, 3 per cent). Seizures were
not reported in any cases. Heart rate greater than 120 bpm was noted in 28 cases (7.5 per cent).
None of the clinical signs seen was considered life-threatening. Age category and
risk period showed significant univariable effects and were included in a multivariable
model. Chocolate exposure was significantly less common in old dogs (odds ratio (OR)=0.42,
95 per cent confidence interval (CI) 0.31 to 0.56, P<0.001) and potentially less common
in middle-aged dogs (OR=0.77, CI 0.59 to 1.01, P=0.058) than dogs under four years
of age. No breed was associated with an increased risk. Chocolate exposure was more
commonly recorded at Christmas (OR=4.74, CI 3.04 to 7.40, P<0.001) and Easter (OR=1.97,
CI 1.36 to 2.86, P<0.001) in this population than at non-festival dates (Fig 1); the
Valentine’s Day and Halloween ORs were not significantly different from 1.0 (OR=0.94,
CI 0.56 to 1.57, P=0.803 and OR=1.55, CI 0.97 to 2.46, P=0.065, respectively). Sources
of chocolate included bars and boxes (often gift selections) of chocolate (35 cases),
Easter eggs (31 cases), chocolate cake (22 cases), liqueurs (5 cases), chocolate rabbits,
Santa Claus figurines, Advent calendars and Christmas tree decorations (10 cases),
as well as one case involving a hot chocolate drink. Dogs ingested chocolate oranges
(15 cases) and Toblerone (6 cases) and in one case, both (six of each). Chocolate
co-ingestion alongside raisins (three cases) and single cases of paracetamol, ibuprofen,
xylitol and onion were noted without evidence that these caused disease. While chocolate
doses were often small, exceptions included ingestion of a garden of Easter eggs hidden
for a large party of children. Documented treatments included activated charcoal (121
cases), apomorphine (114 cases), intravenous fluid therapy (12 cases) and anti-emetics
(31 cases, usually following apomorphine). Activated charcoal therapy often followed
induced emesis but in 65 cases, it was the sole therapy. Theobromine dose was noted
or could be inferred from chocolate dose details in 185 narratives of which 75 narratives
(41 per cent) reflected non-toxic doses (less than 20 mg/kg).17 In 34 of these cases,
patients were still given apomorphine as a safety measure.
FIG 1:
Weekly count of chocolate exposure consultations (blue line, left axis) with odds
ratio for presenting with chocolate intoxication during given celebration periods
(bars±95% CI, right axis). Note: Easter occurs in different weeks each year.
Here the authors describe significant peaks of chocolate intoxication, most notably
at Christmas and to a lesser extent Easter, presumably reflecting the enhanced availability
of seasonally-related chocolate such as Easter eggs, chocolate Santa Claus figurines
and Christmas tree decorations, possibly in the hands of younger members of society.
Peaks of chocolate exposure around Valentine’s day and Halloween described in German
and US reviews4 6 were not seen in the UK, perhaps reflecting alternative romantic
gift choices (or more fastidious curation by their recipient) and different festival
priorities although data to support this conjecture were not available. Use of apomorphine
in cases where theobromine dose appeared to be non-toxic probably reflects a belief
that the low risk of toxicity in these cases outweighs that of emesis but runs contrary
to recent recommendations which point out the lack of evidence for use of emetics
in these cases.17
Chocolate ingestion has a unique seasonal pattern which merits highlighting this risk
to clients, particularly in the run-up to Christmas and Easter as chocolate becomes
more accessible within the household. Given the frequent use of emetics in animals
with documented non-toxic doses of theobromine, further research into the risks and
consequences of emetic therapy is indicated.