Allergic reactions to
eating coconut have been reported, but are relatively rare. By contrast,
contact allergic dermatitis to coconut products is more common. Sensitisation
to coconut pollen has been reported.
Coconut is a useful food
The coconut palm tree is a
native of the tropics. The fruit (seed) of the palm is known as the coconut.
The coconut has great economic value, as the outer fibrous husk can be used to
make ropes and mats, the white inner flesh can be eaten, and the milk drunk.
Coconut derived products are also added to many foods including cakes, some
chocolates and lollies, and are used in some infant formulae. They are also an
ingredient of some cosmetics, shampoos and soaps.
Allergies occur to peanut, tree
nuts and coconut
Allergic reactions to
peanut and tree nuts are relatively common, estimated to occur currently in
around 1/100 infants and 1/200 to 1/500 adults. By contrast, allergic reactions
to coconut are relatively rare. Few cases of allergic reactions from eating
coconut products have been reported, including one case of severe stomach upset
in a baby fed coconut containing infant formula. The other cases reported
have been those of serious allergic reactions (anaphylaxis). Of these cases,
some have been found to be allergic to tree nuts like walnut and hazelnut as
well as coconut, and allergic responses have been found to similar proteins
present in both types of foods, a concept known as cross-reactivity. Others
have been allergic to coconut only.
Food proteins trigger food allergy
The substances triggering
allergic reactions to food are proteins. If a person is allergic to one protein
present in one food only (such as coconut, dairy products,
hen's egg) then an allergic reaction can only occur if they eat that one food.
Allergies may occur to one or many
foods
The proteins that trigger
allergies to egg, dairy products or peanuts are very different. A person
allergic to proteins in dairy products may have problems with dairy products,
but not necessarily other foods. People allergic to dairy (cow's milk) products and egg
are considered to be unlucky enough to be allergic to multiple proteins within
different foods, not the same protein in different foods.
Cross-reactivity is a difficult
concept
Cross-reactivity means
that a similar protein is present in a range of different foods. If the same
protein is present in several foods, then that person may have allergic
reactions to any food containing that protein. Examples of
cross-reactivity include people allergic to similar proteins present in hen's
egg and duck eggs; or cow's milk and goat's milk; or cashew nut and pistachio
nut.
Cross-reactivity is not easy to
predict
In the same way that
different animals have hearts, lungs and muscles, very different looking foods
may have similar structures and proteins. Unfortunately, it is sometimes
difficult to predict whether a person will be allergic to one unique
protein allergen present in one food only, or several similar
cross-reactive proteins present in multiple foods, simply
based on whether foods have a similar appearance.
For example, peanut and
tree nuts (like almond, brazil nut or cashew) make look and taste much the
same, yet the proteins present in peanuts are generally considered to be very
different to those in tree nuts like almonds, cashews and so on. That means
that one can be allergic to peanut only, tree nuts only, or any combination of
peanut, a few tree nuts, or anything that looks or tastes like a peanut or tree
nut.
Coconut allergy is relatively rare
Coconut is a very
different plant from peanut or tree nuts. The presence of the letters
"nut" does not mean that coco-"nut" will trigger an
allergic reaction in people allergic to peanut or tree nuts. The relative
frequency of allergy to peanut and tree nuts (relatively common) compared to
those allergic to coconut (very rare) would suggest that the risk of coconut
allergy in an individual known to be allergic to peanut or tree nuts is very
low, so much so that allergy testing to coconut is not considered as routine.
At the present time there are no published studies examining how often people
allergic to peanut or tree nuts are also allergic to coconut.
The limited knowledge that we have would suggest that the risk is very low. So
what to do if you are worried?
Allergy testing to coconut
At the time of writing,
commercial extracts of coconut are not currently available for skin prick
testing in Australia or New Zealand, and currently no single coconut allergen
is available for blood allergy testing either. If you have concerns about the
risk of allergic reactions to other foods (like coconut or other foods), ask
your medical specialist Allergist / Clinical Immunologist) about
whether skin prick allergy testing or blood allergen specific IgE testing
to coconut has become available.
Contact dermatitis to coconut is
more common than food allergy
Coconut-derived products
(such as coconut diethanolamide, cocamide sulphate, cocamide DEA, CDEA) can
cause contact allergic dermatitis, present in cosmetics including some hair
shampoos, moisturisers, soaps, cleansers and hand washing liquids. As with any
contact dermatitis, an itchy blistering rash may arise a day or two after
contact with the allergen, and take several days to resolve. If contact
dermatitis to coconut products is suspected, then patch testing is an
appropriate method for diagnosis.
©
ASCIA 2010
The
Australasian Society of Clinical Immunology and Allergy (ASCIA) is the peak
professional body of Clinical Immunologists and Allergists in Australia
and New Zealand.
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