**3.5 Multiple food allergies in AD**

#### **Multiple sensitisation to foods in IFA**

Multiple sensitisation with foods has not been generally considered a possible cause of AD; this is another point that can easily confuse clinicians and patients. The prevalence of data describing multiple food allergies in published studies provides an estimate of multiple food allergy prevalence [7, 13]. In a study of food allergies in a highly atopic group of children, all of whom had atopic dermatitis and 50% of whom had concurrent asthma or allergic rhinitis, 57% reacted to two or three foods during double-blind, placebo-controlled food challenges [17]. Most children in this subset had positive skin prick tests (SPTs) to several foods, although only approximately one third of positive tests correlated with positive food challenge [13]. However, few children reacted to more than three foods [18]. Five foods (eggs, peanuts, milk, wheat, and soy) accounted for approximately 60% of the positive clinical responses in this study [19].

More than 500 random serum samples were evaluated for specific IgE against six common food allergens (milk, eggs, wheat, soy, peanuts, and cod) [17]. They addressed that having evidence of IgE-mediated sensitisation to a food does not necessarily imply a true food allergy. This study found that 27% of children were sensitised to more than one of the six foods. The main limitation of this retrospective study was that information regarding clinical reactivity to foods was not available; therefore, it is not known how many of these patients were truly allergic to more than one food.

A recent study examining the prevalence of multiple food allergies found that most (>70%) food-allergic children were allergic to or were avoiding multiple foods [17]. On average, each child was avoiding three or four foods or food groups. These children were generally very atopic, with 56% showing atopic dermatitis, 47% having allergic rhinitis, and 38% having asthma. Thus, highly atopic children may be at greater risk for allergies to multiple foods.

#### **Sensitisation to multiple foods in AD**

Although food allergies are not the only cause of AD, in many cases AD is caused by multiple food allergies. Over 50% of AD patients also exhibited NFA to a mean of 2.8 food items [18]. Moreover, IFA co-exists simultaneously with AD and NFA [7]. Interestingly, in most cases, patients with isolated IFA did not have AD. From these results, it seems clear that NFA is the major type of food allergy in AD, although IFA is the aggravating cause of AD.
