DISCUSSION
In the present study, we found that most of children with AD were
sensitised to at least 1 food allergens, and those who were sensitised
to a greater number of FAs had more severe AD phenotypes and greater
epidermal integrity impairment. Moreover, SCORAD score and SCH level
could predict FS in children with AD.
Most children with AD (90%) in the present study were sensitised to at
least one of the tested FAs; this prevalence was higher than those
reported by Moghtaderi et al.8 (51%) and
Yuenyongviwat et al.9 (60%). However, those studies
investigated smaller numbers of FAs (20 and 8 allergens, respectively),
compared with our study.8,9 Additionally, other
studies in children aged < 15 years showed that the prevalence
of FS ranged from 30% to 40%,10,11 below the
prevalence in our study. This difference may have occurred because FS is
more frequent in young children and can be outgrown. In another study,
the prevalence of FS in children with AD ranged from 20% to
80%.12 These findings suggest that FS is more common
than previously reported in children with AD, particularly among such
children aged < 5 years. Additionally, the number of FAs
investigated in each study and the ethnicity of the study population
could affect FS prevalence.
We found that cow’s milk protein (60%) was the most common sensitised
FA, followed by egg white (49%), beef (31%), almond (27%), egg yolk
(26%), and peanut (26%). Similar results were reported by Moghtaderi
et al.8. Another study also showed that egg, cow’s
milk, and peanut were the most prevalent allergens in children with AD
who were sensitised to FA.13 However, a study in an
American population showed that egg and peanut were the most prevalent
FAs.14 Differences in common sensitised FAs among
studies could be related to differences in ethnicity, age, local food
customs, and dietary habits among study populations. In Vietnam and
other Asian countries, cow’s milk proteins and egg appear to be the most
common FAs in children.
We also examined features of co-sensitisation among the tested FAs and
found that egg white and beef had the highest prevalence of
co-sensitisation, such that 71.4% of children sensitised to egg white
were also sensitised to beef; 58.3% of children sensitised to beef were
also sensitised to egg white. This prevalence was higher than that
reported previously, which showed that 28.5% of AD children who were
sensitised to egg white also exhibited beef
sensitisation.15 The prevalence of co-sensitisation to
cow’s milk and cow’s milk protein ranged from 75% to 91.7% in children
with AD who were sensitised to goat’s milk. Therefore, in clinical
practice, caution should be exercised when introducing cow’s milk to AD
children who have had allergic reactions to beef and/or goat’s milk.
Additionally, children with AD who were sensitised to egg yolk
demonstrated a high prevalence (92.3%) of sensitisation to egg white;
consequently, caution should be exercised when introducing egg white to
children with AD who have had allergic reactions to egg yolk.
To our knowledge, this is the first study in Vietnam to evaluate the
association between FS and epidermal layer impairment. We found that in
children with AD, lesional skin had significantly higher TEWL levels and
lower SCH levels compared with non-lesional skin. Additionally,
participants with moderate-severe AD had significantly higher TEWL
levels and lower SCH levels in lesional skin, compared with participants
who had mild AD. These findings were consistent with the results of
Montero-Vilchez et al.16, who showed that impaired
skin barrier function in the lesional skin was associated with AD
severity.
The damaged epidermal barrier (indicated by increased TEWL levels and
decreased SCH levels) in patients with AD could enhance FA penetration
and induce FS.2 In the present study, participants who
were sensitised to more FAs exhibited higher TEWL levels and lower SCH
levels, compared with non-sensitisers or children sensitised to fewer
FAs. A previous study involving children aged 1–2 years with AD and FS
revealed higher TEWL levels than non-sensitisers.14Although these findings suggest a clear association between FS and
epidermal barrier impairment, the causative relationship between these
factors cannot be determined using data from cross-sectional studies.
We found that the number of sensitised FAs was positively associated
with AD severity, as determined by SCORAD scores. Compared with
non-sensitisers, children with AD who were sensitised to FAs such as
egg, cow’s and goat’s milk proteins, beef, pork, chicken, rice, and
others (Table S1) had more severe AD. This was consistent with the
findings of Wolkerstorfer et al.17. Additionally,
Leung et al.18 showed that decreased expression of
filaggrin and increased TEWL levels in the skin of individuals with AD
could facilitate FS into deeper skin layers. Subsequent exposure to FAs
via damaged skin could trigger an inflammatory response, leading to
enhancement of AD severity.2 Other studies showed
strong associations among FS, food allergies, and the severity and
chronicity of AD.8,18 Consequently, those findings
indicate that FS could be associated with epidermal barrier impairment
and subsequently AD severity in children.
There is currently no clinical guidance regarding the appropriate time
to evaluate FA in patients with AD. The results of previous studies have
suggested that FS is associated with severe and persistent
AD.19 In the present study, we analysed the ROC curves
of SCORAD scores, as well as the utilities of SCH and TEWL levels, in
terms of predicting FS in the study subjects. We found that SCORAD
scores and SCH levels in lesional skin had moderate predictive value for
sensitisation to cow’s milk, egg, almond, beef, peanut, and goat’s milk
in children with AD. SCORAD scores and SCH levels in lesional skin had
the highest predictive value for sensitisation to peanut and the lowest
predictive value for sensitisation to cow’s milk. However, TEWL levels
were not useful for predicting FS in the present study. The SCORAD
assessment and the measurements of TEWL and SCH levels are easy,
non-invasive procedures that are safe for children. Our findings suggest
that clinicians should consider assessing FS in children with
moderate-severe AD and/or low SCH levels in lesional skin.
The limitations of the present study include the inability to perform a
follow-up assessment because of the cross-sectional design. Furthermore,
we did not perform an oral food challenge test to determine food
allergies. The age range of our study participants was also limited
because we did not include children aged < 1 year. Thus, the
study results are not representative of children with the highest
prevalence of AD (i.e., children aged < 6 months).
In conclusion, FS was common in children with AD; it was closely
associated with AD severity and epidermal barrier impairment.
Evaluations of food sensitisation should be considered for children with
moderate-severe AD and/or low SCH levels.