Someone asked about peanut sensitization during pregnancy and breastfeeding.
I think you are probably refering to the 1998 article in the British Journal
of Medicine entitled: "Women warned to avoid peanuts during pregnancy and
lactation."
I found an interesting discussion of this issue at:
http://www.allerg.qc.ca/peanutallergy.htm#sensitization
Kathleen Fallon Pasakarnis, M.Ed., IBCLC
Peanut allergy: where do we stand?
John Weisnagel, M.D.
Sensitization to peanuts
-possible during pregnancy, probable during breast feeding:
The British Medical Journal, June 27th, 1998 published a letter entitled
"Women warned to avoid peanuts during pregnancy and lactation." that came
from the Department of Health, Committee on Toxicity of Chemicals in Food,
Consumer Products and the Environment, Wetherby, North Yorkshire. According
to John Warner, professor of child health at Southampton University and a
member of the government's working group on peanut allergy, there appears to
be a "link between maternal consumption of peanuts and peanut products and
earlier onset and increasing prevalence of allergy. Evidence from aborted
fetal samples shows that from the second trimester onwards fetuses are
capable of producing an allergic reaction. There are several theories on how
sensitization occurs. Some research shows that antigens from the mother can
cross the placenta, whereas other work suggests fetuses can swallow IgE from
the amniotic fluid, causing sensitization 31.
Following the June 27th, 1998, article in the British Medical Journal, a
comment was published in The Lancet by Pamela W Ewan, July 4th, 1998,
entitled "Prevention of peanut allergy" in which she notes that the
Committee's report said that pregnant women "may wish" to avoid eating
peanuts...she stresses the importance of peanut allergy as a common cause of
anaphylaxis...its prevalence having increased substantially32 ...regarding in
utero (during pregnancy) sensitization, there is a lack of convincing
evidence from prospective studies that manipulation of the maternal diet
during pregnancy has a lasting effect on the development of food allergy.
Indirect data suggest that lactation is a more likely route of primary
sensitization, but this point remains to be established34.
In the Aug 29th, 1998 issue of The Lancet, Deborah E Fox, Gideon Lack, as
well as Richard S H Pumphrey, Phillip B Wilson, and Amolak S Bansai, respond
to Pamela Ewan's commentary. The first letter agrees with Ewan's call for
further studies 'so that these public health measures can be soundly
based'...the UK guidelines ..have caused distress to mothers with
peanut-allergic children. The second letter authors suggest that the advice
of the Committee be extended to all nuts 35.
In a Feb 1999 study done in Cape Town, South Africa79, it was shown that:
mothers who consumed peanuts more than once a week during pregnancy were more
likely to give birth to a peanut-allergic child than mothers who consumed
peanuts less than once a week.
Peanuts or peanut butter was introduced into the child's diet from a
significantly younger age in the peanut-allergic subjects.
There was a positive correlation in the peanut-allergic subjects between age
of introduction of peanuts and age at the onset of symptoms.
Exclusive breast feeding did not protect against the development of peanut
sensitization.
Peanut allergy is associated with an increased risk of sensitization to other
foods. (posted Aug. 6th, 1999)
In the June 2000 of the Anaphylaxis Network Newsletter, Dr Peter Vadas, past
President of the Anaphylaxis Foundation of Canada, and the Medical Director
of the Regional Anaphylaxis Clinic at St Michael's Hospital in Toronto,
writes in his article on 'The Process of Sensitization', "A study just
completed in my laboratory has shown that peanut protein does, in fact, pass
from the maternal diet via the bloodstream into breast milk. Using a very
sensitive assay for peanut allergens, we tested samples of breast milk for
the presence of peanut protein at various times after consumption of dry,
roasted peanuts by a group of volunteers. The two major peanut allergens
associated with anaphylaxis were detected in breast milk within one to three
hours after ingestion in approximately 50% of the volunteers. These data
confirm the previously unproven notion that some infants may become
sensitized by exposure to peanut protein through breastfeeding." The study Dr
Vadas refers to has just been published in the April 4th, 2001 issue of the
Journal of the American Medical Association 115 (posted April 14th, 2001) Dr
Vadas continues, "However, the story is not quite so simple. The
concentration of peanut protein, timing of exposure and frequency of exposure
may lead to either allergic sensitization or to tolerization. The latter
process actually protects against allergies. In some cases, exposure to
peanut protein in breast milk may actually protect against later development
of peanut allergy. At this stage, it would be overly simplistic to suggest
that all lactating women avoid peanut products during breastfeeding. While
this may protect some children from peanut sensitization, it may predispose
other children to acquiring peanut allergy by preventing the process of
tolerization. Instead, it may be more prudent for lactating mothers to avoid
peanut products while breastfeeding hight risk infants, namely those who have
a strong family history of allergies or those who already have a first degree
relative with peanut allergy. (posted July 26th, 2000)
The concept of tolerization, or tolerance, was touched upon by Drs Gideon
Lack and Jean Golding, in their comments regarding Pamela W. Ewing's article
entitled 'Clinical study of peanut and nut allergy in 62 consecutive
patients: new features and associations.' BMJ 1996;312:1074-8 (27
April)...."exposure to peanuts and other food allergens during lactation and
childhood may be important in the development of immunological tolerance and
may prevent allergic sensitisation to these foods...avoidance measures would
serve only to reduce exposure to peanuts to low levels, and this could
pardoxically increase allergic sensitisation to peanuts; low dose exposure to
allergens (rather than high dose exposure) favours production of IgE, and as
little as 2 µg of inhaled allergen a year may be sufficient to induce
allergic sensitisation via the airways." (posted July 26th, 2000)96
Other possible sources of sensitization:
How about peanut oil in vitamin A and D preparations? According to a Feb 1999
Swedish study, sensitization to peanut during childhood through consumption
of vitamin A and D in oil-based solution seems unlikely.78 (posted Aug. 6th,
1999)
Another suggestion is that sensitization might occur by contact with the
skin, through the application of creams containing arachis (peanut) oil for
eczema, or nipple ointments in mothers during breast feeding as reported by
Lack G, Fox DES, Golding J, at the AAAA&I Annual meeting in Washington, DC,
March 1998. (posted Aug 6th, 1999)
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