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Peanut allergy

  1. Top of page
  2. Peanut allergy
  3. Previous government advice
  4. A systematic review of the new evidence
  5. Translating the science into new advice
  6. Box 1: Summary of government advice on eating peanuts
  7. The need for careful communication of the new advice
  8. Further research
  9. Conflict of interest
  10. References

Peanut allergy receives widespread attention because very small amounts can trigger severe, sometimes fatal, allergic reactions in susceptible people. As many as 1 in 55 children in the United Kingdom (UK) show evidence of an allergic reaction to peanut (Hourihane et al. 2007); and peanut allergy is the most common cause of severe allergic reaction to foods (Hourihane et al. 1997). Unlike many food allergies, which tend not to persist beyond childhood, peanut allergy is often a life-long problem and can cause severe anaphylactic reactions to tiny amounts of peanut protein.

True IgE-mediated allergic reactions such as peanut allergy require prior exposure and sensitisation of the immune system to the allergen. Because peanut-allergic infants tend to show symptoms on their first known exposure to peanut, it has been suggested that sensitisation to peanut is acquired by the foetus during pregnancy, or by an unrecognised dietary exposure or by non-oral (skin or respiratory) routes. For this reason, whether exposure to peanut in early life (maternal exposure in pregnancy or dietary exposure in infancy) is linked to a greater risk of childhood peanut allergy is a question that has been addressed by scientific research.

Previous government advice

  1. Top of page
  2. Peanut allergy
  3. Previous government advice
  4. A systematic review of the new evidence
  5. Translating the science into new advice
  6. Box 1: Summary of government advice on eating peanuts
  7. The need for careful communication of the new advice
  8. Further research
  9. Conflict of interest
  10. References

In 1998 the UK government issued precautionary advice to mothers whose children have a family history of allergic diseases, that they may wish to avoid peanut consumption during pregnancy and breastfeeding and avoid giving their children peanuts/peanut products until they reach 3 years of age (COT 1998). The precautionary advice was based on recommendations from the Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT), which advises the UK government. These recommendations were in part based on the concept that intrauterine immunological sensitisation can occur and increases the likelihood of subsequent atopic disease. This concept was primarily based on reports of in vitro proliferative and cytokine responses by allergen-stimulated cord blood mononuclear cells (Miles et al. 1996) and the demonstration that such responses were associated with subsequent atopic disease (Warner et al. 1994).

COT's recommendations have since come under scrutiny as further scientific evidence on the development of peanut allergy and other food allergies in children has emerged. In particular, more human studies have become available in this area, and studies on cord blood are thought to be less relevant. Therefore, in 2007–2008, the Food Standards Agency (FSA) commissioned a systematic review of the literature on food allergy published since 1999, in order to assess the relevant evidence base since COT issued its recommendations in 1998. The systematic review was conducted by the British Nutrition Foundation with the help of an Advisory Group, and evaluated studies that aimed to investigate dietary food allergen consumption or avoidance behaviour in early life (maternal and early childhood diets) and subsequent development of food allergy, with a particular focus on peanut allergy. Non-dietary exposure to peanuts, e.g. cutaneous or environmental exposure, was also reviewed. The review included both human and animal studies, and also a review of evidence investigating the response of cord blood mononuclear cells to allergens.

A systematic review of the new evidence

  1. Top of page
  2. Peanut allergy
  3. Previous government advice
  4. A systematic review of the new evidence
  5. Translating the science into new advice
  6. Box 1: Summary of government advice on eating peanuts
  7. The need for careful communication of the new advice
  8. Further research
  9. Conflict of interest
  10. References

The full methods and results of the systematic review on early life determinants of peanut allergy have been published by Thompson et al. (2010); the major results from human studies relevant to advice to reduce the risk of peanut allergy are summarised here.

Studies considering peanut exposure during pregnancy and breastfeeding and the development of peanut sensitisation or allergy were limited to two small case control studies, both with around 25 cases of peanut allergy. While one of these studies looked at peanut sensitisation (Frank et al. 1999) and the other allergy (Lack et al. 2003), both measured peanut consumption by the use of questionnaires. Both studies reported non-significant differences in the development of peanut sensitisation or allergy when they compared the children of mothers who consumed peanuts more or less often in pregnancy and/or during breastfeeding, after adjustment for confounders.

One other cross-sectional study made reference to maternal peanut consumption and peanut sensitisation in infants (Hourihane et al. 2007). The authors reported that there was no statistically significant difference in sensitisation to peanuts in children of mothers who changed their peanut consumption (reduced or avoided, i.e. as a response to the COT recommendations) compared with children of mothers who did not change their peanut consumption.

The relationship between dietary exposure to peanuts during childhood and subsequent development of peanut sensitisation or allergy was assessed in two multifaceted trials, which included peanut avoidance as one of the features of the intervention arm (other allergen-avoidance advice was also issued in the intervention arms, such as house dust mite avoidance) (Chan-Yeung et al. 2005; Arshad et al. 2007), and in one case-control study (Frank et al. 1999). Both intervention studies reported no statistically significant differences between the intervention and control groups with regards to peanut sensitisation. The case-control study reported on mean age of introduction of peanuts or peanut butter in children aged 0–3 years. On average, peanuts were introduced earlier in peanut allergy cases compared with controls; the result was statistically significant (P = 0.03) but it was not adjusted for other factors. Overall, the evidence from these human studies does not suggest that dietary exposure to, or avoidance or delaying introduction of, peanuts changes the likelihood of subsequently developing peanut sensitisation or allergy.

The number of human studies investigating the effects of non-dietary exposure to peanuts on the development of sensitisation and allergy is also scant. One study reported an increased risk of peanut allergy in children who were exposed to skin creams containing peanut oil (Lack et al. 2003). However, further studies are necessary to clarify whether topical exposure to peanut protein presents a real risk with respect to sensitisation.

The small number of human studies found that have investigated peanut exposure during early life and risk of subsequent peanut sensitisation or allergy clearly highlights the lack of evidence available in this area. Furthermore, the evidence reviewed in the systematic review was not of high quality (Thompson et al. 2010).

Translating the science into new advice

  1. Top of page
  2. Peanut allergy
  3. Previous government advice
  4. A systematic review of the new evidence
  5. Translating the science into new advice
  6. Box 1: Summary of government advice on eating peanuts
  7. The need for careful communication of the new advice
  8. Further research
  9. Conflict of interest
  10. References

The findings from the systematic review were submitted to the COT, which concluded that its previous advice on peanut allergy is no longer supported by the current scientific evidence. UK Health Ministers were then advised to revise the government's precautionary advice to mothers to become in line with the conclusions of the COT.

Before new advice to mothers was published, consumer research was commissioned by the FSA and the Department of Health, to explore appropriate wording of the new advice. This was considered important because, as discussed later in this article, COT's previous advice had not been interpreted by health professionals and parents in a consistent way. The overall aim of the research was to explore consumer, health professional and other relevant stakeholders' understanding of the draft revised government advice on peanut consumption when planning conception, during pregnancy, breastfeeding and until 3 years of age, and to capture any feedback regarding whether and how the revised advice could be improved before it is issued to the public. The research was carried out by the people partnership and is published on the FSA website (FSA 2010). The qualitative research comprised group discussions with mothers-to-be (both with and without a history of allergy in the family) and in-depth interviews with health professionals and other stakeholders.

In August 2009, the government issued new advice about eating peanuts during pregnancy, breastfeeding and the first few years of life, in relation to the risk of developing peanut allergy in childhood. The new advice (see Box 1) was published on the FSA website and ‘The Pregnancy Book’, ‘Birth to Five’ and ‘Ready Steady Baby’ publications were used to disseminate the advice further.

Box 1: Summary of government advice on eating peanuts

  1. Top of page
  2. Peanut allergy
  3. Previous government advice
  4. A systematic review of the new evidence
  5. Translating the science into new advice
  6. Box 1: Summary of government advice on eating peanuts
  7. The need for careful communication of the new advice
  8. Further research
  9. Conflict of interest
  10. References

Pregnant or planning to have a baby

  • • 
    If you would like to eat peanuts or foods containing peanuts (such as peanut butter) during pregnancy, you can choose to do so as part of a healthy balanced diet, unless you yourself are allergic to them or unless your health professional advises you not to.
  • • 
    You may have heard that some women, in the past, have chosen not to eat peanuts when they are pregnant. This is because the government previously advised women that they may wish to avoid eating peanuts during pregnancy if there was a history of allergy in the child's immediate family. But this advice has now been changed because the latest research has shown that there is no clear evidence to say that eating or not eating peanuts during pregnancy affects the chances of your baby developing a peanut allergy.

Breastfeeding or have an infant under 6 months old

  • • 
    If you would like to eat peanuts or foods containing peanuts (such as peanut butter) when you are breastfeeding, you can choose to do so as part of a healthy balanced diet, unless you yourself are allergic to them or unless your health professional advises you not to.
  • • 
    You may have heard that some women, in the past, have chosen not to eat peanuts when they are breastfeeding. This is because the government previously advised women that they may wish to avoid eating peanuts when they are breastfeeding if there was a history of allergy in their child's immediate family, in case small amounts of peanut in their breast milk increased the chance of the baby developing peanut allergy. But this advice has now been changed because the latest research has shown that there is no clear evidence to say that eating or not eating peanuts when breastfeeding affects the chances of your baby developing peanut allergy.
  • • 
    Government advice to all mothers is that you should try to exclusively breastfeed your baby until about 6 months of age. Breastfeeding provides benefits to both mothers and babies.
  • • 
    If you have a child under 6 months and are not breastfeeding, then there is no reason why you should avoid consuming peanuts or foods containing peanuts, unless you yourself are allergic to peanuts or have been advised not to consume them by your health professional for other reasons.

Introducing your child to solids

  • • 
    You should try to exclusively breastfeed your baby until about 6 months of age.
  • • 
    If you choose to start giving your baby solid foods before six months [after talking to your health visitor or general practitioner (GP)], don't give them any peanuts, other nuts (such as hazelnuts, almonds, walnuts), seeds, milk, eggs, wheat, fish, shellfish or foods containing these ingredients until after 6 months of age. This is because these foods can sometimes trigger development of a food allergy.
  • • 
    When you give these foods to your baby for the first time, it is a good idea to start with one at a time so that you can spot any allergic reaction. If you think your child is having an allergic reaction, you should seek urgent medical attention. Common symptoms of an allergic reaction include one or more of the following: coughing; dry, itchy throat and tongue; itchy skin or rash; diarrhoea and/or vomiting; wheezing and shortness of breath; swelling of the lips and throat; runny or blocked nose; sore, red and itchy eyes.
  • • 
    You may have heard about previous advice to avoid giving a child food containing peanuts before 3 years of age, if there was a history of allergy in the child's immediate family. This has now changed because the latest research has shown that there is no clear evidence to say that this will help to reduce the risk of your child developing a peanut allergy.
  • • 
    If your child already has a known allergy, such as a diagnosed food allergy or diagnosed eczema, or if there is a history of allergy in your child's immediate family (if the child's parents, brothers or sisters have an allergy such as asthma, eczema, hayfever, or other types of allergy), then your child has a higher risk of developing peanut allergy. In these cases, you should talk to your GP, health visitor or medical allergy specialist before you give peanuts or foods containing peanuts to your child for the first time.
  • • 
    Whole peanuts or whole nuts should never be given to children under five because of the risk of choking.

This information is adapted from the Food Standards Agency's website. See: http://www.food.gov.uk/safereating/allergyintol/peanutspregnancy

The need for careful communication of the new advice

  1. Top of page
  2. Peanut allergy
  3. Previous government advice
  4. A systematic review of the new evidence
  5. Translating the science into new advice
  6. Box 1: Summary of government advice on eating peanuts
  7. The need for careful communication of the new advice
  8. Further research
  9. Conflict of interest
  10. References

There is evidence that COT's previous advice on peanut consumption in early life was not effectively communicated (Dean et al. 2007; Hourihane et al. 2007). Although it was intended to be aimed specifically at women and children with a family history of allergic disease, in practice, it was often interpreted as relevant to women and children in general. Consequently, those not in the target group avoided peanuts unnecessarily. Second time round, it is imperative that health professionals are well informed about the interpretation of the new advice, and well equipped to answer questions from parents and parents to be. The revised advice specifically refers parents of children with another allergy or a family history of allergy to health professionals for advice. Although these children will be at greater risk of peanut allergy, there is no scientific evidence to indicate that this risk will be reduced if peanuts are avoided. Health professionals need to have the knowledge available to handle such discussions. Indeed the qualitative consumer research commissioned by the FSA (2010) highlighted that many consumers felt that much more should be done to provide the relevant advice proactively to individual people in a tailored fashion and at the right time for them. It was felt to be particularly important to ensure that mothers who already have a child get access to the new information, because these women are otherwise likely to follow the ‘old’ advice that they received during their previous pregnancy. It is clearly important that the uptake and communication of any new advice is monitored and evaluated.

A factor that further emphasises the need to evaluate how the new advice is interpreted by both health professionals and mothers is the commonly incomplete avoidance of peanuts among pregnant women who choose to avoid peanuts, demonstrated by Hourihane et al. (2007), which means that they may be exposed to very small amounts. This is of interest because animal studies suggest that oral exposure to low amounts of peanut protein may induce sensitisation, whereas higher amounts may result in tolerance (Strid et al. 2004). Thus, if these findings are shown to be applicable to humans, incomplete avoidance of peanuts could prove harmful rather than protective against the development of peanut allergy or sensitisation in the child. However, further studies are needed to confirm whether this is the case in humans.

Further research

  1. Top of page
  2. Peanut allergy
  3. Previous government advice
  4. A systematic review of the new evidence
  5. Translating the science into new advice
  6. Box 1: Summary of government advice on eating peanuts
  7. The need for careful communication of the new advice
  8. Further research
  9. Conflict of interest
  10. References

The impact of maternal exposure and timing of introduction of peanuts into the infant diet on allergic outcomes remains an active area of research. Studies are underway that have the potential to provide more definitive data by 2013. An example is the Learning Early About Peanut Allergy (LEAP 2006) study, which is a clinical intervention study testing the hypothesis that high dose and early introduction of peanuts into infant diets will induce oral tolerance and prevent the development of peanut allergy. Mechanistic analyses of samples from the LEAP cohort could help develop an understanding of the processes in the developing immune system that lead to the acquisition of oral tolerance to peanuts, peanut sensitisation and peanut allergy.

In the meantime, the available evidence does not support avoidance of peanuts in maternal diets during pregnancy or lactation, or avoidance or delayed introduction of peanuts in the diets of children.

References

  1. Top of page
  2. Peanut allergy
  3. Previous government advice
  4. A systematic review of the new evidence
  5. Translating the science into new advice
  6. Box 1: Summary of government advice on eating peanuts
  7. The need for careful communication of the new advice
  8. Further research
  9. Conflict of interest
  10. References