Peanut Allergy is usually a life-long allergy affecting 1.9% of Australian infants.
A recent study in the USA shows that 1.1% of the general population have peanut
& tree nut allergy. Peanut is the commonest cause of death due to foods.
Three key points characterize peanut and nut hypersensitivity:
The reactions can be extremely violent and life threatening with minimal exposure.
The amount of allergen required to induce allergic symptoms may be as low as 0.10mg
(1 peanut is approximately 180mg) equivalent to 1/2000th of a peanut.
Symptoms have been known to develop after kissing someone who has eaten peanuts
Peanut allergy is likely to persist throughout life (especially if there is strongly
positive skin prick test reaction to peanut & if associated with other food
Peanut (legume) allergy is frequently associated with other non-legume (e.g., nut)
and seed allergy. Peanut and tree nut allergic reactions coexist in one third of
peanut allergic patients.
The commonest manifestation of peanut allergy is with acute urticaria (hives) following
exposure. However, some patients may rapidly develop angioedema, bronchospasm and
Relative frequency of symptoms of peanut Allergy from a study in France:
Atopic dermatitis 40%
Urticaria & Angioedema 37%
Anaphylactic shock 6%
Digestive symptoms 1.4%
Peanut Reaction to first exposure
In one study 81% of children reported reaction on first exposure to peanut. This
raises the question about how sensitisation occurs and is important to remember
when giving advice on preventing allergies.
Peanuts are among the most allergenic foods. The peanut allergen is a glycoprotein.
It is present in raw & roasted peanuts since it is heat stable. It may contaminate
crude (cold pressed) peanut oil.
Sources of Peanut Allergens
Peanuts are widely used in Western & Oriental cooking.
Peanut, or traces, if present in a food, must be declared on the food label, even
if peanut is not the primary ingredient.
Very good studies have shown that traces of peanut protein are found in cold pressed
(crude) but not warm pressed peanut oils.
Peanut oil is sometimes called groundnut or arachis oil. Unfortunately manufacturers
sometimes label foods as containing "vegetable oil" which may well contain
Avoid any foods, cosmetics, creams or ointments that contain or are made with Arachis
oil. Some nipple creams used while breast feeding have been known to contain arachis
oil, as do some ointments used to treat atopic eczema.
Other common sources of peanut include:
- Peanut, groundnut, arachis
- Peanut butter
Baked goods – Pastry, biscuits, cookies,
crackers, health bread
Asian foods – Thai, Chinese & Indonesian
- Vegetarian foods
- Cold pressed (crude) peanut oil
- Muesli and breakfast Cereals
- Ice creams
- Mixed Nuts, Marzipan
- "Natural" flavouring
- Egg rolls
- Health foods – bars & sweets
Diagnosis of Peanut Allergy
A history of an allergic reaction occurring shortly after exposure to peanuts is
very suggestive. However, this should always be confirmed with a
There have been several
cases where the wrong nut has been assumed, with serious consequences. Also, tree
nuts should be tested in view of the frequent coexistence of these allergies.
is very rarely needed in peanut anaphylaxis. In doubtful
cases or to confirm that the peanut allergy is outgrown (after borderline SPT or
RAST) then it may be necessary.
Treatment of Peanut Allergy
If Anaphylaxis has occurred or in patients with previous immediate
systemic reaction following peanuts (especially asthmatics) and when the CAP RAST
is above the threshold level of 15kUa/l, all the precautions for Anaphylaxis
should be taken.