Swedish Study Investigates Food Allergy Increases in Children But Big Questions Remain
- by Rishma Parpia and Barbara Loe Fisher
- Published
- Risk & Failure Reports
An estimated 1 in 13 children in the United States now have food allergies, a 50 percent increase in the incidence of food allergies between 1997 and 2011. Food allergy researchers have suggested there are several factors contributing to this increase, including shifts toward more processed diets, insufficient levels of vitamin D from limited sun exposure, and the “hygiene hypothesis.” Researchers forwarding the hygiene hypothesis argue that the cleaner environments children live in today limit children’s exposure to microbes, which can cause their immune systems to react more strongly to certain foods.1
A 2025 study, which was conducted in Sweden and published in Pediatric Allergy and Immunology, supports the theory that delaying the introduction of allergenic foods to infants could be a factor contributing to the increase in food allergies.2
Sweden’s New Guidelines Aimed At Reducing Allergy Risks
Since 2019, the Swedish National Food Agency has recommended that parents breastfeed infants for at least the first six months and begin introducing solid foods around six months of age, but no earlier than four months. The recommendation encourages parents to start with small tastes of various foods and gradually increase portion sizes throughout the first year, regardless of the child’s potentially higher risk of developing food allergies indicated by a family history of allergies.
Recent research indicates that these updated feeding guidelines have been successfully adopted by families across Sweden. As a result, a wider range of foods, including legumes and peanuts, are being introduced to infants at an earlier age than was previously suggested before recommendations were revised.
There is evidence now that early introduction of eggs and peanuts can help reduce the risk of babies developing allergies to these two foods; however, there are still outstanding questions about other allergenic foods and the optimal timing of introducing them to babies.3
Researchers in Sweden studied the food allergy data on 2,060 babies by having parents complete a questionnaire that measured their infant’s diet diversity at six and nine months. The questionnaire asked how often babies ate 14 different foods, including six common allergens: wheat, egg, fish, dairy, nuts (especially peanuts), and soy.4
The study found that introducing a variety of foods to babies at nine months can reduce the risk of food allergies by 18 months, especially for babies with eczema or no family history of allergies. It showed that offering more types of food at nine months, regardless of how often they were eaten, was linked to a lower allergy risk; however, introducing more foods at six months did not seem to have the same effect.5
The researchers also emphasized the importance of offering plant-based foods, such as fruits, vegetables, and legumes, which may help reduce the risk of food allergies. They noted that previous studies did not consider how often babies ate certain foods, but stated that this study’s focus on food frequency could provide valuable insights into preventing food allergies.6
While the Swedish feeding guidelines recommend introducing solid foods at around six months, the study found that starting solids before four months might help babies develop a more varied diet by six or nine months. However, starting solids too early, before four months, did not directly lower the risk of food allergies.7
The study also found that babies with eczema who were given a more varied diet at nine months seemed to have a lower risk of developing food allergies. This suggests that early exposure to different foods can help babies build tolerance, especially if they are at higher risk for food allergies,8 although introducing common allergens like peanuts or eggs before six months does not clearly reduce this risk.9
Evidence That Food Proteins in Vaccines May Cause Food Allergies
In addition to lab altered microbes contained in live attenuated virus and inactivated bacterial and viral vaccines and mRNAs shots, there are many excipients in biological products labeled vaccines, including adjuvants; preservatives; antibiotics; mineral salts; cell proteins; medium nutrients; DNA and other residual mediums and by-products; protein purifiers; buffers; emulsifiers, lipids and surfacants.10
In 2015, Vinu Arumugham published an article in Journal of Developing Drugs providing evidence for a potential association between food proteins and other excipients in childhood vaccines and immune system sensitization that can cause anaphylactic reactions, as well as the development of food allergies. Pointing out that people can have allergic reactions to influenza vaccines containing egg protein, and that there is evidence for a causal relationship between gelatin containing DTaP vaccine and gelatin allergies, and that another DTaP vaccine ingredient – casamino acid – “is dervived from milk proteins and results in allergy to dairy,” Arumugham said:
There are no specifications limiting allergen content in vaccines approved for use in the United States. In other words, no safe level has been established or enforced for allergens contained in vaccines. Vaccine excipient makers such as sorbitol, Polysorbate 80 manufacturers also have no limits on residual allergens in their injectable grade products. Since there are no limits, suppliers do not test for allergens in production. Further, residual allergens that may be present in the excipients are not even listed in the vaccine package inserts.11
Arumugham also pointed out that “pertussis toxin and aluminum compounds act as adjuvants,” with both of these ingredients included in whole cell DPT and acellular DTaP/Tdap vaccines. He said:
Injecting food proteins along with these adjuvants increases the immunogenicity of the food proteins that are present in the vaccines. With up to five shots administered simultaneously, numerous food proteins and adjuvants get injected at one time. This increases the probability of sensitization.
Research Needed To Identify All Causes of the Food Allergy Epidemic Among Children
Although introduction of foods known to cause allergy to babies at an earlier age appears to be one strategy that helps prevent development of food allergies in children, other researchers emphasize that identifying genetic variants, epigenetic and other environmental factors that predispose toward and make some individuals more susceptible to food allergy must be included in basic science and epidemiological research investigating all possible causes of the dramatic increases in food allergy among children over the past three decades. Authors of a 2021 study concluded:
The risk factors for food allergy (FA) include both genetic variants and environmental factors. Advances using both candidate-gene association studies and genome-wide approaches have led to the identification of FA-associated genes involved in immune responses and skin barrier functions. Epigenetic changes have also been associated with the risk of FA. Little is known about possible modifying effects of genetic variation on the associations between environmental factors and FA… Future studies of gene-environment interactions, gene-gene interactions, and multi-omics integration may help shed light on the mechanisms of FA, and lead to improved diagnostic and treatment strategies.12
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