Question:
Can anyone please shed some light on a situation for me......
would a person with a sulfa allergy react to something with a sulfate
salt?
Scenario: child received cortisporin otic suspension, which contains
polymixin B sulfate, neomycin sulfate and hydrocortisone.
Since using the ear drops, the child has developed a rash
reaction in his ear. Although NKA was noted in his
profile,
we were later told he has a sulfa allergy.
Has anyone came across this before? What exactly is someone allergic
to if the have a sulfa allergy? Would they have a reaction to anything
with - -S in it's
molecular structure?
Answer:
First a "sulfa" allergy is generally meant to be an allergy to
compounds in the sulfonamide group. These molecules are more complex
than a common "sulfate". Sulfonamides include a benzene ring as
well as a "sulfonamido" group in their structures. They are employed
in various ways, many as anti-infectives. A "sulfate" refers to as "salt" form of some compound. The "sulfate"
portion of polymyxin-b sulfate is simply a sulfur molecule with some
oxygen and hydrogen attached.
Now the question. Did the child receive any of the following products
_orally_ to treat the ear infection? Bactrim, Septra, or Pediazole?
These _all_ contain sulfamethoxazole (a sulfonamide anti-infective)
and are often given along with an ear drop to treat ear infections.
They are often the culprit in "sulfa" allergies in children.
I suppose it is possible that the child is allergic to the element
sulfur, but that is not something I have ever seen.
Since the reaction was localized to the ear, it is probably more likely
that one of the components of the ear drop caused the reaction.
The problem with these "combination" preparations, is that when there is
a local reaction to the product, it is difficult to pinpoint the actual
allergen. It could be the polymyxin-b, the neomycin, or the
hydrocortisone (allergies to hydrocortisone are not all that unusual,
even though it is used to _treat_ allergic reaction). It could even be a
reaction to one ofthe solvents, or "inactive" ingredients in the ear
drop. IMHO the most likely culprit is the neomycin, which, in my
experience causes local irritation in a significant number of patients.
However, if the reaction is _only_ the result of the ear drop, it
is most likely NOT a "sulfa" allgery.
Sulfates are simple salts, and have nothing to do with sulfa drugs,
which are antibacterial compounds which contain an aromatic sulfonamide
structure. Sulfonamides can produce a delayed hypersensitivity reaction,
which might include a rash or swelling or flu-like symptoms, just to
name a few symptoms.
Neomycin not infrequently causes contact sensitivity; that's a more
likely reason for the rash.
