Flouting widely held beliefs that yellow jacket stings
have less effect early in the season and that most people
can outgrow a dangerous allergic reaction to a sting,
allergists at Johns Hopkins have concluded that the sting
severity is determined not by the calendar but by the
species of insect doing the stinging.
"As far as stings go, some yellow jackets are worse
than others," said David Golden, an associate professor of
allergy and
immunology at the School of Medicine. "Because we've
found that the severity of an allergic reaction is related
to the species of yellow jacket, it's important for people
to understand that they can have wildly different reactions
depending on which species stings them and that getting
stung once without an allergic reaction does not guarantee
that a more serious reaction will not happen with a later
sting."
Published in the Journal of Allergy and Clinical
Immunology, the study by Golden and his research team
involved 111 patients who had all tested allergic to yellow
jackets. The researchers performed 175 test stings with two
different species of yellow jackets and closely monitored
the study participants for physical symptoms resulting from
the stings, such as flushing, changes in vital signs,
dizziness, shortness of breath and hives.
Golden's original research goal was to find out why
some people have allergic reactions to stings while others
do not, but over time, he said, he began to notice that
subjects were having fewer reactions to a particular
species of yellow jacket, leading the researchers to
restructure and analyze the data they had collected at the
three-year mark. They found that allergic reactions were
much more common, and nastier, with the yellow jacket
called Vespula maculifrons than with the one named Vespula
germanica. These are the two most common species in the
eastern United States, and most people can't tell them
apart.
The researchers also checked whether yellow jacket
stings were stronger at the end of the summer. They found
that the stings in the first half of the summer caused the
same number of allergic reactions as the stings in the last
half of the summer. Once in July and then again in October,
they also collected venoms from Vespula germanica and
Vespula maculifrons, and tests showed no difference in the
ability of the early- and late-summer venoms to cause
allergic reactions.
The likelihood of a severe reaction was 41 percent in
those who had a history of bad reactions and who were stung
with Vespula maculifrons and 15 percent when stung with
Vespula germanica. Those who had experienced only mild
sting reactions in the past and who were stung by Vespula
maculifrons had a 17 percent chance of a subsequent
reaction and only a 3 percent chance when stung by Vespula
germanica.
"Our results show that people who had the worst
reactions in the past have the most to worry about from
future stings," said Golden. "They shouldn't be fooled into
thinking that they will be safe from all future stings just
because they have no reaction to a particular yellow jacket
sting."
Allergists recommend that those who are susceptible to
severe reactions should be immunized to protect them
against the allergy. Allergy shots with purified venoms
(venom immunotherapy) give almost total protection from
allergic reactions to stings.
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