To the Editor: In their report of a child with peanut allergy who developed sunflower seed allergy, Hsu and Katelaris caution against marketing claims of “safe alternatives” in allergic children.1 Their report also raises practical issues for those advising the parents of a child with food allergy: what is the risk of a new allergy developing; should a child with peanut or tree nut allergy avoid similar foods as well; and will food avoidance prevent new allergy from developing?

The natural history of peanut and tree nut allergy is for polysensitisation to develop over time. One study demonstrated that, in children younger than 2 years with peanut or tree nut allergy, 19% were sensitised and 2% were clinically reactive to more than one nut.2 By the age of 14 years, the percentages had risen to 72% and 47%, respectively. This has led to people with peanut or tree nut allergy being advised to avoid all nuts and seeds.2 Strategies commonly advised to reduce the risk of allergy developing are to avoid food allergens and to delay the introduction of allergenic foods until the age of 2 years, but evidence to support their effectiveness is limited,3 particularly for preventing food allergy.4

While studies in infants at high risk of allergic disease have reported an increased risk of eczema with early introduction of solids (before the age of 3–4 months),3 and a protective effect against asthma and eczema with the avoidance of environmental and food allergens in the first 6 months of life,4 a recent systematic review found “no strong evidence to support the association between early solid feeding and the development of persistent asthma, persistent food allergy, allergic rhinitis, or animal dander”.5 Furthermore, there is currently no evidence that avoidance strategies applied beyond 6 months of age are effective for allergy prevention, and provisional evidence that such strategies might actually promote sensitisation and food allergy rather than tolerance.6

So how should we advise patients?

The peanut and tree nut avoidance strategies advised will be largely dictated by:

• choking hazards in infants;

• the risks of cross-contamination in commercially prepared foods; and

• the potential for confusion in young children (and caregivers) trying to differentiate one “nut” product from another.

Regarding the risk of developing new food allergy, we should advise patients that:

• new allergies may develop with time;

• this risk is unpredictable;

• we have little evidence to recommend avoidance beyond the age of 6 months as an effective preventive strategy; and

• parents should not be optimistic (given the current state of knowledge) that such strategies will prevent new sensitisation once food allergy has developed.