April,
 (Feel free to share this with the mom). I would say 99% it is not the
benadryl. I would say 99% it's not the mammary constriction syndrome,
because I would say that causes musculoskeletal pain and not decreased
supply (although I guess you could say that any nerve impingement could
affect supply).
I would say it's something else. It could be a baby thing or a mommy thing.

These things seem relevant:
baby was "extremely fussy" at breast and mother began pumping - how soon
did that start? We all know that babies can "coast" on mom's early
hormonal-driven supply and the history shows baby did well early. Does the
baby have any airway symptoms? Does the baby have positional issues?
Torticollis? Does the baby have a submucosal cleft, posterior tongue-tie?
These are the things I would try to look for.

When mother's pump, we all know that it is more on a "schedule" and less on
"demand" like a baby, and maybe our bodies need those cluster feeds? So I
definitely beleive that for most mothers who are just pumping and not
suckling the baby, the supply will downregulate over time, so that is
another factor. I think most babies who are directly suckling the breast
would nurse more than the number of times she is probably pumping each 24
hr day, and more than the two 4-hr night stretches. Please do not take this
as anything negative against the mom, because I know she is heroically
trying to preserve breastfeeding. I am just an objective observer looking
for all the factors. And usually these sort of dramatic decreases in supply
have multifactorial causes.

Re the allergic reaction: what was it like? Could it possibly have been a
virus? Rashes are very common with viruses. Fifth's disease? What I am
thinking is a systemic illness and coupled with the above factors just
knocked the supply down? Could even be something more serious like
autoimmune (Lupus and Lupus-related like Sjogren's).

Laurie Wheeler RN MN IBCLC
Mississippi USA

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