Tree nut and peanut allergies are relatively common and there is evidence that they are increasing. Although botanically unrelated, tree nut and peanut allergies commonly co-exist. Reactions to tree nuts, similar to peanuts, can be life-threatening and may occur with very small doses.

The allergic response involves the release of histamine and other inflammatory markers that can have effects seen in the skin, gastrointestinal, respiratory and cardiovascular systems of the body. 

Common allergy symptoms include:

  • hives (rash and itching on the skin) 
  • eczema (red itchy inflamed skin)
  • vomiting.

Severe symptoms are more uncommon and include:

  • difficulty in breathing due to swelling of the mouth and throat
  • anaphylaxis – dilation or constriction of blood vessels. This results in swelling which can restrict airways and/or cause a serious drop in blood pressure (anaphylactic shock), which may ultimately cause death.

Food allergy occurs in around 5-10% of children and 2-4% of adults in Australia and New Zealand.

Prevalence data for nut allergy and in particular tree nut allergy is limited. Based on self-reported allergy in primary school aged children, allergy to any tree nut has been reported as 1.8-2% in children. For adults, studies indicate 1.1-2% of the population.

The most common triggers of food allergy are egg, cow’s milk (dairy), peanut, tree nuts, sesame, soy, wheat, fish and other seafood.  However, almost any food can cause an allergic reaction, including fruits. Those most likely to cause anaphylaxis are peanuts, tree nuts, shellfish, milk and egg.

Allergies to peanut, tree nut, seeds and seafood are less likely to be outgrown, tending to be lifelong allergies.

Treatment for a nut allergy is to totally avoid the nut you are allergic to

Diagnosis

A true (IgE-mediated) food allergy is diagnosed through a detailed medical history, physical examination and allergy testing. Allergy tests include a skin prick test (SPT) or blood test to measure IgE levels and, when necessary, an oral food challenge. Diagnosis should always be made by a medically trained allergy specialist.

Nuts in pregnancy

The majority of evidence suggests exposure to nuts during pregnancy and via breastfeeding do not increase, and may actually decrease the risk of allergy in children [1, 2].

In May 2016, the Australasian Society of Clinical Immunology and Allergy (ASCIA) revised their Infant Feeding and Allergy Prevention guidelines based on a consensus agreement by participants in the Infant Feeding Summit hosted by the Centre for Food and Allergy Research (CFAR) in May 2016, as a result of current published scientific research [3]. Recommendations specifically related to peanuts and/or tree nuts include:

“Exclusion of any particular food (including foods considered to be highly allergenic) is not recommended during pregnancy or whilst breastfeeding as this has not been shown to prevent allergies.”[3]

Recent studies have shown that delayed introduction of solid foods to babies (after 12 months of age) can increase the chance of developing food allergies.  For example, a Danish study showed that maternal intake of peanuts and tree nuts were inversely associated with asthma and allergic rhinitis. The large-scale longitudinal study surveyed over 60,000 mothers’ mid pregnancy, when their children were 18 months old and again when they were seven years old [2].

Introduction of nuts to infants

For otherwise healthy infants, the National Health and Medical Research Centre (NHMRC) recommends exclusively breast feeding and then the introduction of solids when the infant is ready at around 4-6 months of age (but not before 4 months) with no specific age recommendations for any individual foods [4]. Many studies provided evidence to support this, suggesting that prolonged avoidance of solids or specific allergens is not protective and may in fact be a risk factor with regard to allergic diseases or food allergy [5, 6]. 

The ASCIA infant feeding guidelines [3] recommend introducing foods according to what the family usually eats, regardless of whether the food is considered to be a common food allergen, at around 4-6 months of age. Nut butters, pastes and flours can be introduced at this time, just like other foods. As a guide, mix a small amount (¼ teaspoon) of smooth peanut butter/paste into your baby’s usual food (such as vegetable puree). If there is no allergic reaction, gradually increase the amount, such as ½ teaspoon the next time. Do not give whole nuts or nut pieces until around five years to reduce the risk of choking.

Nuts in schools

Both ASCIA and many state government health departments (e.g. NSW Department of Health) do not recommend blanket food bans or attempts to prohibit the entry of particular foods, such as peanuts and tree nuts. They state that such bans are difficult to enforce, and may also produce a false sense of security for students with allergies and their parents. There is also a lack of evidence to support the effectiveness of such measures. 

References

  1. Willers, S.M., et al., Maternal food consumption during pregnancy and asthma, respiratory and atopic symptoms in 5-year-old children. Thorax, 2007. 62(9): p. 773-9.
  2. Maslova, E., et al., Peanut and tree nut consumption during pregnancy and allergic disease in children-should mothers decrease their intake? Longitudinal evidence from the Danish National Birth Cohort. J Allergy Clin Immunol, 2012. 130(3): p. 724-32.
  3. ASCIA. Guidelines: Infant feeding and allergy prevention. ASCIA 2016. http://www.allergy.org.au/patients/allergy-prevention/ascia-guidelines-for-infant-feeding-and-allergy-prevention.
  4. NHMRC, Eat for Health: Infand Feeding Guidelines Summary, N.H.a.M.R. Council, Editor. 2013, Commonwealth of Australia: Canberra.
  5. Koplin, J.J., et al., Can early introduction of egg prevent egg allergy in infants? A population-based study. J Allergy Clin Immunol, 2010. 126(4): p. 807-13.
  6. Du Toit, G., et al., Early consumption of peanuts in infancy is associated with a low prevalence of peanut allergy. J Allergy Clin Immunol, 2008. 122(5): p. 984-91.
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