Well, with allergies what works depends on the individual and on the type
and severity of the response.  A friend who was a past FML member had to
stop having anything to do with ferrets because of massive acute asthma
attacks, and we had to help someone place some ferrets rapidly when a
child in the family did that.  We're not talking tiny reactions here or
even truly serious discomfort without immediate danger, but "Get to the
hospital NOW" level ones.  There is one case on record of a man who
almost died due to a sudden onset of anaphylactic reactions to ferrets.
As far as I know he's the only one documented reacting that way to being
near them though certainly those reactions have been documented in the
past to horses, dogs, and especially to cats.
 
Now, I am not saying that there aren't people who invent "allergies" to
dump pets (a supposition which becomes even greater when the animals
haven't even had vet care), but there are a few people who have
experienced truly dangerous levels of reactions which even combinations
of antihistamines, asthma preventative meds, steroids, and epi inhalers
can't off-set well enough for them to around ferrets, and it does need to
be respected that some rare people are in life-threatening danger from
them for this reason.
 
Now, there is one additional point to note: it has been noticed here many
times that a number of people who do not react to other ferrets do react
to whole male ferrets, and that this seems to be more common among those
who are allergic to cats.
 
So, reactions to ferrets in general appear to be pretty unusual,
especially if severe, but reactions to whole males, including strong
reactions seem to be more common, and avoiding whole males may be wise
for those who are allergic to cats, especially if that reaction is a
strong one.  Cat allergies are rather common and more common that
allergies to dogs.  If a person reacts to whole male ferrets the
individual will NOT necessarily react to other ferrets so the individuals
have to decide for themselves whether to try a challenge.
 
Allergies can not always be controlled.  Sometimes the response is just
too massive for meds to handle.  That is why there are those who die of
asthma each year (somewhere in the thousands in the U.S. if memory serves
but it has been a very long time since I read the stats so if you want
numbers check me because I could be off in either direction by 10x.  If
I am remembering right hundreds die each year of anaplylactic reactions.
(There are some far more rare types of fatal allergic reactions like
dermal necrosis but they don't fit in here except to illustrate that
allergies can be very dangerous and very hard to control.)  So, sometimes
when a ferret or other animal is surrendered due to allergies the problem
is very real and immediately seriously dangerous.
[Posted in FML issue 4270]