Vaccines are controlled inoculations
fragments of infectious agents of
inactive infectious agents induce the
primary immune , the
formation of specific B
lymphocytes against the .
Therefore the organism produces
and becomes prepared
to antigens when exposed to
infections by those agents.

allergies the humoral immune
is sensitized (makes antibodies
specific memory B lymphocytes)
some common environmental
substances recognized as
antigens. For , pollen-derived
substances, dust particles,compounds
in foods or in , etc.
may be recognized antigens
triggering the primary and
creating an immune against
them that then causes of
allergy. The the individual is
exposed those substances the more
is the immune reaction.

IgE antibodies that cause
bind to receptors of called
mastocytes whose cytoplasmis of
histamine granules. The
mastocyte bond causes these to
release a great of histamine in
the , stimulating inflammation
and generating allergic symptoms
and signs. this reason allergy is
with antihistamines, drugs that
the histaminic reaction.
Exacerbated reactions, for
example, in to some
medicines like and sulphus, may
cause shock, a severe
clinical that sometimes leads
to .