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Peanuts – A new baby food?

Disha Kumar





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What’s the big deal about peanut allergies?                                                                                              

Over the last several years, there have been great efforts to make society more aware of the peanut allergy.  Pediatricians emphasize that peanuts only be introduced to children after age 3 for fears of peanut allergy.  However, the prevalence of peanut allergies in children has been increasing rapidly, even resulting in many schools banning the ever-popular peanut butter and jelly sandwich for lunch in fears of children going into anaphylactic shock.  Food allergies are responsible for 30,000 severe allergic reactions and 200 deaths annually (  About 1.5 million Americans are allergic to peanuts ( 


Why does this number seem to be growing?  Are there any measures parents can take to prevent their children from becoming allergic to peanuts?  While the peanut allergy is still a bit of a mystery to scientists, claims have been made that exposing children to potential allergens and small amounts of peanut products early on actually helps to prevent the development of allergies.   


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The Science Behind Allergies


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Various foods, medications, dust mites, pet dander, insect stings, and latex can cause allergies in children and adults.  Specific allergies are diagnosed through skin-prick tests or blood tests.  When the body is exposed to an allergen, immunoglobulin E (IgE) antibodies specific to that allergen cause mast cells to release histamine, mast cell granule proteins, prostaglandins, leukotrienes, and cytokines into the body (Online Demonstration:  These chemicals cause an inflammatory response in the body that defines a sensitivity to certain foods, resulting in allergy symptoms.  Symptoms can range from itching and tingling to breathing difficulties, swelling, hives, vomiting, diarrhea, lower blood pressure, and even death.  This is also referred to as anaphylaxis, which is a “sudden, severe, potentially fatal, systemic allergic reaction that can involve various areas of the body (such as skin, respiratory tract, gastrointestinal tract, and cardiovascular system)” ( 


Nobody really knows what causes peanut allergies, but it is evident that young children, especially those with a family history of various allergies, are most at risk.  It is still debatable if pregnant women or mothers who breastfeed are likely to pass on small quantities of peanut proteins, increasing the risk of their babies developing peanut allergies (  Allergies can also be caused through direct contact with peanuts, foods or other products that may have been prepared with or in the presence of peanuts, or inhalation of peanut dust (


While the best way to prevent anaphylaxis to peanuts is to avoid them altogether, there are a few treatments to reduce peanut allergy symptoms.  Antihistamines can control and relieve mild allergic reactions.  For more severe reactions, emergency epinephrine injections (Epipen®, for example) can be administered (  But, could all of this be prevented if children were just introduced to peanuts early?




Can we really prevent peanut allergies altogether?


In the last several years, peanut allergies have doubled in the United States and other countries that recommend peanuts be avoided until age three.  In contrast, the prevalence of peanut allergies is ten times lower in parts of Africa and Asia where children are frequently exposed to peanuts (  Scientists have begun to contemplate whether these regions of the world might really have the right idea in terms of preventing a potentially fatal allergy.   


Previous findings have suggested that early exposure to an undeveloped immune system, the indigestible peanut protein in roasted nuts, and contact with peanut oil-containing creams could cause the development of peanut allergies in children

(  While this may be true, recent approaches to allergy prevention focus on desensitizing the immune system.  Instead of keeping young children in germ-free, sanitary environments, it might actually be important to expose them to some dirt and potential allergens in order to train their immune systems and limit reactivity (  This stems from the hygiene hypothesis, which suggests that children in large families or those who are frequently around animals and nature are less susceptible to immune disorders like allergies since they are more likely to encounter infectious agents at a young age (  For instance, ironically enough, hay fever is more common in urban areas than in rural or underdeveloped parts of the world.


So does this mean that if we allow for the “pig pen effect” to occur and start introducing babies to small amounts of peanuts, children will lead healthier lives?


Does the research back this up?


Medical research is slowly beginning to focus in on this question as the prevalence of allergic diseases in childhood continues to rise.  Current scientific evidence is lacking in providing a decisive conclusion on the desensitization towards peanuts, but a few studies have begun to study the hygiene hypothesis and the effects of early exposure.  I will discuss three such studies, followed by an analysis of current evidence on the desensitization to peanuts.  


The Hygiene Hypothesis and Early Exposure to Allergens


In more scientific terms, Romagnani (2004) supports the hygiene hypothesis and offers that the reduced microbial burden during childhood has resulted in an increased prevalence of allergy.  This results in the reduced activity of the T regulatory cell and increased immune allergen-specific response from the type 2 T helper cell, which in turn leads to an allergic response. 


Gereda, et al. (2000) compared the home environments and presence of bacterial toxins of three different areas: urban homes, farm homes and barns, and homes in rural India and Peru.  Measuring the levels of environmental endotoxins, or bacterial toxins, along with the prevalence of allergies in children in that type of environment, it was shown that greater endotoxin levels in rural areas and developing countries help to explain the lower prevalence of asthma and allergies in children.  Thus, an environmental endotoxin has the potential to provide an allergy-protective effect. 


In relation, Hesselmar, et al. (1999) studied whether the early exposure to cats or dogs, in addition to family size, protect against future allergy development.  The prevalence of allergies and background factors such as the number of family members, presence of pets, and frequency of infections were analyzed in 1991 and 1996.  2,481 children between the ages of 7 and 9 were studied in 1991, and then a subgroup of 412 children were followed from 1992 to 1996 at 12-13 years of age.  With an increase in the number of siblings and exposure to pets in the first year of life, children had a lower incidence of allergic rhinitis at 7 to 9 years of age, and a lower incidence of asthma at 12-13 years of age.  Therefore, exposure to pets during infancy could have a protective effect on the development of allergies later in life.  In Western society, large families and several pets are uncommon, which may explain the increasing prevalence of allergies in this part of the world.


Desensitization to Peanuts


Using these studies to compare the hygiene hypothesis and the benefits of early exposure to peanuts, current research predicts that an early exposure to peanuts can in fact prevent allergies in children.  However, there is very little data to support this prediction.


In her study, Pamela W. Ewan (1996) investigates the nature of peanut allergy in 62 patients.  These patients ranged from 11 months to 53 years of age.  Using skin-prick tests, peanut allergy was found to occur most frequently in young children, Ewan concludes that sensitization to peanuts occurs in young children and that peanuts and nuts should be avoided until age 7 in order to prevent allergy.  Gideon Lack and Jean Golding (1996) submitted an opposing response to Ewan’s article, stating that there was no evidence behind her conclusion.  Instead, they point out that other countries that consume large amounts of peanuts have lower allergy rates, and that exposure to peanuts during lactation and childhood may be essential to developing tolerance.  While no evidence is presented to support these points either, current research is studying the development of tolerance to peanuts in infancy.  


At the annual American Academy of Allergy, Asthma, and Immunology in March, 2006, Adam T. Fox, MD of Imperial College presented a new study hypothesizing that peanut exposure would result in sensitization, but small amounts of peanut may actually protect atopic children.  Survey questions for this study included information about how much peanut the mother ate during pregnancy, in addition to how much peanut was consumed by other family members during the child’s first year of life.  Children were divided into three groups: children with peanut allergy, children with egg allergy, and children with no allergies.  The children with allergies consumed 77.2g of peanuts per week, and the children with no allergies consumed 29.1g.  This study found that low levels of peanut can actually protect allergic children, and that mothers who eat peanuts during pregnancy or breastfeeding do not cause the development of peanut allergy in their children.


For those who already suffer from peanut allergies, some comfort can be found from a study by Skolnick, et al. (2001), which supports that tolerance to peanuts can be regained.  Although it was thought that peanut allergies are rarely outgrown, this study performed skin tests and immunoassays on 223 patients aged 4 to 20.  48, or 21.5%, of these patients originally thought to have sensitivity to peanuts passed an oral peanut challenge that determined they had outgrown their allergy.  These patients also had a low peanut IgE level and few other allergies, versus those with higher peanut IgE levels and a greater number of allergies (please refer to Figure 1 below).  While this study addresses the importance of reintroducing peanuts after an initial allergic reaction to older children, it also emphasizes the importance of exposure and building tolerance and immunity over time.




Have we found a solution to reduce the occurrence of peanut allergies?


While there have been positive results in studies that explore the early exposure of common allergens such as pet dander and dust, a generalization cannot be made about peanuts and early exposure.  Peanut allergies are still a bit of an enigma, and current research is only beginning to tackle the issue of early exposure to peanuts.  For now, it is best to follow pediatricians’ advice and wait until children are 3 years old to introduce peanuts.  Until then, steer clear of the peanut butter and jelly sandwiches.





Ewan PW. (1996). Clinical study of peanut and nut allergy in 62 consecutive patients: new features and associations. British Medical Journal, 312, 1074-8.


Food. (2006). Retrieved September 15, 2006 from The Food Allergy and Anaphylaxis Network,


Food Allergy Frequently Asked Questions. (2006). Retrieved September 17, 2006 from American Peanut Council,


Fox, AT. (2006). Risk of Peanut Allergy Associated with High Household Exposure to Peanut in Infancy. Retrieved September 12, 2006 from American Academy of Allergy, Asthma, and Immunology,


Frequently Asked Questions. (2006). Retrieved September 15, 2006 from The Food Allergy and Anaphylaxis Network,


Gereda, JE, et al. (2000). Levels of Environmental Endotoxin and Prevalence of Atopic Disease. Journal of the American Medical Association, 284(13), 1652.


Golding, J and Lack, G. (1996). Reduced Exposure Might Increase Allergic Sensitisation. British Medical Journal, 313, 300.


Hesselmar, B, et al. (1999). Does early exposure to cat or dog protect against later allergy development? Clinical and Experimental Allergy, 29, 611-617.


Hygiene Hypothesis. (2006). Retrieved September 16, 2006 from Wikipedia,


The Mayo Clinic Staff. (2006). Peanut Allergies. Retrieved September 14, 2006,


Redfern, Julie. (2002). Health-e-Weight for Women: Special Topics and Articles. Retrieved September 17, 2006 from Brigham and Women’s Hospital,


Romagnani, S. (2004). The Increased Prevalence of Allergy and the Hygiene Hypothesis: Missing Immune Deviation, Reduced Immune Suppression, or Both? Immunology, 112, 352-363.


Sternberg, Steve. (2006). To Head Off Allergies, Expose Your Kids to Pets and Dirt, Really. Retrieved September 12, 2006 from USA Today,


Skolnick, HS, et al. (2001). Natural History of Peanut Allergy. Journal of Allergy and Clinical Immunology, 107(2), 367-374.


Weisnagel J. (1998). Peanut Allergy: Where do we stand? Retrieved September 12, 2006,