Question:
My 4 mo son had a GI visit today for breastfeeding colitis. The dr feels it
is probably caused by allergies, but wants him to have skin tests done to
confirm or refute that before she considers further investigations.
Does anyone know anything about the risks associated with skin tests in
infants, and whether they are reliable?
Answer:
When our son was 4 months the doctor did allergy tests on myself instead of the
baby, since the foods affecting him were obviously coming from breast milk
(that was all he was given) and so were probably things I was allergic to. I
also found it helped if I reduced my intake of milk (which didn't show up in
any tests). The doctor was reluctant to do tests before 3 - 3.5 years, but I can't remember
why now.
Skin testing for allergies is usually not recommended for
infants and small children til about age 4, since the
immune system is not fully developed. There is the
danger of an allergic reaction to skin tests, or it
could cause a sensitivity to develop. However blood tests for allergy could be done. See:
http://babyparenting.about.com/library/Users/uc061101a.htm
"Traditionally, allergy tests were performed by
allergists using skin testing which involves pricking
the skin to apply allergens, with a raised welt
indicating sensitivity. Skin testing, however, carries
the risk of an allergic reaction, and is not
recommended for young children, seniors, those
taking antihistamines, or those with dermatitis and
other skin conditions.
Previously, allergy blood tests were less accurate
than skin testing, but a new blood test,
ImmunoCAP™, is not only as accurate as a skin test
in determining specific allergies, it is the first and
only allergy test approved by the FDA to test them
quantitatively. Family physicians, pediatricians and
allergy specialists can draw a blood sample that is
analyzed in a laboratory. Health professionals then detect
the presence of IgE, an antibody circulating in the blood
when the body is fighting an allergen. " I certainly agree with you that skin tests are not in order here, but
let me make some comments about the comments.
It takes at least several months of contact with inhalant allergens
before a significant IgE response can be mounted. Four months is too
soon for "hay fever" to develop: by the time the IgE response has
occured that first season is over. We do not expect ever to see hay
fever type reactions until at least the child's second season, but it
can happen by then, and positive skin tests to pollens may be seen
shortly after that first season; that is, within the child's second
year. If it appears that there is true inhalant allergic rhinitis
showing before age one, only house dust or the family pet would be
suspected, because of the continuous and prolonged exposure, and I have
found confirmation from skin prick tests before the first birthday. The
most likely cause of allergic rhinitis within the first year would be
food allergy, and skin testing for food allergy is controversial at
best. Pediatricians are often not trained in allergy and therefore
think of skin testing as a rather barbarous procedure, and some don't
very much believe in the benefits of allergy investigation and
treatment anyway. These, I believe, are the reasons that parents are so
often told that their child is too young for testing.
Large and itchy skin tests may develop in the infant, as in the
adult, but it should be remembered that there have been no fatalities
reported anywhere in the world's medical literature due to skin scratch
testing since a 1963 fatal reaction to a penicillin test.
Sensitization does not occur due to tests for IgE-mediated allergy.
There is always the danger of this when patch tests are done to
identify the cause of delayed hypersensitivity reactions, and it is for
this reason that testing for poison ivy is never performed.
Skin testing that is done as part of a study to be reported in the
literature is never done on a patient who is receiving antihistamines.
However if allergic symptoms are present at the time of testing, it is
clear that the antihistamines are not suppressing the immediate
reaction and skin tests, though diminished in size, are likely to be
positive. However there is a recent report that children under 6 months of age are
at greatly increased risk of generalized reaction from skin prick tests. Devenney I, Falth-Magnusson K; "Skin prick tests may give generalized
allergic reactions in infants"; Ann Allergy Asthma Immunol 2000 Dec;85(6
Pt 1):457-60.
