A Goossens, K Neyens
Introduction
Allergic
contact dermatitis has not been studied as extensively in children as in
adults. Although there are many
similarities between these two patient populations, the results obtained with
adults cannot always be applied to children.
A child is not simply a small version of an adult but has its own
characteristics.
Allergic
contact dermatitis in children has always been considered rare, and their
eczematous conditions have mostly been attributed to endogenous factors such as
atopic or seborrheic dermatitis, sometimes in association with irritancy
induced by soap, clothing, etc. One of
the reasons for this would be their reduced exposure to environmental allergens
(professional, cosmetic, pharmaceutical).
Some authors also cite a reduced reactivity and sensitization capacity
of children’s skin. As allergic contact
dermatitis was not often suspected in children, little patch testing was
performed. Since the 1980’s, however,
this diagnosis has been more frequently considered. Photo-allergic contact dermatitis does seem to be rare, although
it may also be under diagnosed.
Incidence
of allergic contact dermatitis in an unselected population
Data
regarding the incidence of allergic contact dermatitis in healthy children are
scarce: percentages vary between 13 and 24 %.
Incidence
of allergic contact dermatitis in a selected population
Several
studies have been performed in children suspected of contact allergy or
suffering from atopic or juvenile plantar dermatitis, orofacial granulomatosis,
dyshidrosis, psoriasis, photo-sensitivity, urticaria, or other dermatoses. The studies differ in the number and the age
of the patients investigated, the clinical symptoms, as well as the relevancy
and the incidence of the positive reactions observed. Percentages vary from 3.6 % up to 71 % of the children
tested, with the majority around 40 %.
Other
factors that render comparison of those studies difficult include the different
test populations involved (e.g. the presence or not of atopy, differences in
origin and habits), the variability of the test conditions (materials,
allergens, concentrations, vehicles, reading times), and the interpretation of
the test results, i.e. allergic or irritant.
The question arises whether allergic contact dermatitis in children has
become more frequent in recent years.
Some authors think this is the case.
Incidence
in relation to genetic factors
Professional
and environmental factors are essential but the hereditary background could
also be important.
Incidence
related to sex
While
some authors detected similar incidences in both boys and girls, others
reported on a higher incidence in the girl population. This is especially the case for nickel, and then
after the age of 12. Hormonal factors
may be a contributory factor hereby.
Unlike
some authors, most report an increasing incidence of allergic contact
dermatitis with age and attribute it to an increasing exposure to environmental
allergens. This also applies to the
development of multiple sensitivities. A reduced sensitization potential in
younger children has also been suggested; this has been experimentally. However, several cases of allergic contact
dermatitis in neonates and infants have been described.
The
exposure of children to contact allergens varies throughout the world,
according to, for example, their exposure to certain plants, topical
pharmaceutical products, types of clothing, shoes, etc.
Objects
or materials common to the children’s environment may give rise to some unusual
allergen sources, such as sucked-on objects, for example, which are not at all
rare causes of allergic cheilitis and peri-oral dermatitis (e.g. also due to
rubber allergens), particularly in the younger age group. This also applies to mercurials present in
vaccines and topical pharmaceuticals used to treat abrasions and infections of
the skin. However, nickel, cosmetic
ingredients, and occupational allergens are rather causes of allergy in older
children.
The
clinical characteristics of allergic contact dermatitis are, in general, the
same in children as in adults. It is of
utmost important to perform a detailed anamnesis in order to specify the
environment of the child and of those taking care of it and to examine
thoroughly the topography of the lesions.
Indeed, the localization is often an indication of the allergen or
allergens involved. Based on data
published in the literature, we compiled a list of allergens in relation to
specific body sites. Sometimes the
clinical picture is unusual.
The
association between atopy and allergic contact dermatitis in children is a
controversial subject. The conclusions
drawn differ largely according to the allergens investigated and whether the
incidence of allergic contact dermatitis in atopic children is being
investigated or the incidence of atopy in children suffering from allergic
contact dermatitis. Nickel reactions
are more often seen in atopics, and then mainly in girls, which indicates the
greater importance of sex and ear piercing than atopy as such. One has to stress the irritant properties of
metals and particularly nickel on atopic skin, and, indeed, papulo-pustular
patch test reactions are a frequent.
Patch
testing is indicated not only when a contact allergy is suspected, but also in
case of persistent eczema on specific localizations, such as on the hands and
the feet and around the mouth and also in the peri-umbilical region,
particularly in atopics (nickel!). The
latter group should certainly be tested when multiple exacerbations occur even
when they are treated or when the dermatitis is asymmetrical. Most authors agree that patch testing in
children is safe, the only problems being mainly technical because of the small
patch-test surface, (hyper)-mobility (which may result in loss of patch test
materials), particularly in younger children, and the reluctance of some
parents to allow patch testing. The
following instructions when testing children should be given: test in different
sessions if the test area is very small; should the patches come off, ask the
parents to report it and instruct them not to reapply the patches. It may be necessary to use a stronger
adhesive than usual, but this could be irritating. The application has to be performed as quickly as possible while
the child is distracted; make a diagram of the tested allergens (this applies
for adults, too); inform the parents about the test procedure and the measures
that may be taken to optimize the patch-test conditions.
The
patch test concentrations have been discussed in detail in the literature. Some authors have recommended lower
concentrations, particularly with regard to specific allergens such as nickel
and formaldehyde, mercurials, potassium dichromate, MBT, and thiuram mix. Irritancy problems have been reported with
patch testing, especially in the younger age group. Recent data indicate, however, that the same test concentrations
as in adults should be used, although this is still being discussed. In dubious cases, one might have to retest
with a lower test concentration.
The most frequent allergens in children.
Cobalt
Potassium dichromate
Aluminum
Palladium
Iron (exceptionally)
Many
topical pharmaceutical ingredients have been described as allergens in children
and should certainly not be overlooked.
They include antibiotics, antihistamines, non-steroidal
anti-inflammatory, local anesthetics; and even corticosteroid. Also plant extracts may be responsible. Not only active principles but also other
ingredients may be responsible for allergic reactions in children: emulsifiers
and vehicle, preservative, etc.
Every
individual ingredient may be responsible for cosmetic dermatitis, preservative
agents, perfume components, and so on.
Children often become allergic to cosmetics used by the mother (or the
person taking care of them) and they sometimes themselves use these products,
although this may not always be immediately revealed! Contact and photo-contact allergy to sunscreens may also occur.
Preservative
agents in play gels and plasticine are examples; furthermore allergens in model
kit, glue, and fire-arm accessories, cuddly toys and by balloons (cfr. below)
has been described.
Additives
in the rubber of balloons, in elastic underwear, particularly when bleached, in
rubber sponges used to apply cosmetics, and in gloves. As with balloons, for example, type I
allergic reactions may also occur, sometimes associated with a type IV
reaction. Moreover, a contact urticaria
syndrome induced by natural latex proteins is a frequent finding in such
children, those suffering from spina bifida being particularly susceptible in
this regard. Rubber additives are also
the main allergens responsible for shoe dermatitis (cfr. below).
Shoe
dermatitis generally affects the back of the feet. When the soles are affected, it is generally a juvenile plantar
dermatitis. Mercaptobenzothiazole and
thiuram derivatives, which are present not only in rubber shoes but also in
certain glues, are important shoe allergens.
Other potential culprits are PPD and derivatives, and glues.
Plastic
toys as well as glues have been described as typical allergen sources for
children (e.g. PTBP, epoxy resins), for example also in orthopedic braces.
Children
often come in contact with plants while playing and do not know about their
potential irritant (photo-toxic) or allergenic effects. Many plants have been described as the cause
of such reactions.
“Occupational” allergens
Among
adolescents, certain professional activities are likely to induce
sensitization, particularly in hairdressers and construction workers, and to a
lesser extend in metal workers.
Pre-employment patch testing is not recommended, although some authors
advocate it, particularly with regard to metal allergy.
Allergic
contact dermatitis in children is more frequent than previously thought. Immunological differences between children
(especially neonates) and adults do exist, however, their impact on the clinical
development of contact allergy is still unknown. Although allergic contact dermatitis has occasionally been
observed in neonates, it is generally agreed that the liability to develop
contact sensitization, but certainly also the exposure to environmental
allergens, increase with the children’s age.
Whether
allergic contact dermatitis is more or less frequently associated with atopy is
still controversial. On the one hand,
there is the reduced Th1 response by which atopics are less likely to develop contact
allergy; on the other hand, the damaged skin barrier facilitates allergen
penetration. The possibility of
allergic contact dermatitis in atopic children has to be considered,
particularly if the distribution of the lesions is asymmetrical, when the
dermatitis is located peri-umbelically (nickel!) and when the dermatitis
persists when being treated. As with
adults, the anamnesis and localization of the dermatitis are crucial for the
diagnosis of allergic contact dermatitis; certain contactants and/or habits
that are characteristic for the child or the adolescent, may be responsible for
unusual clinical presentations though.
Patch
testing in children is safe and most authors now agree that irritant reactions
are not frequently observed (except in atopics, particularly with metals) and
that probably the same patch test concentrations as in adults can be used.
The
most important allergens observed in this population are metals such as nickel
(sometimes associated with cobalt), particularly in girls, which is attributed
to the popularity of cheap jewelry. (To
what extend hormonal factors play a role is still a matter of debate). Mercury and derivatives are still used as
antiseptic agents in certain countries, but the allergic reactions observed,
even in young children are not often clinically relevant; this is particularly
true for thiomersal, for which vaccines have been regarded as the main
sensitization source. (Allergy does not
seem to be contra-indicated for future vaccinations though, provided the tip of
the needle is not contaminated and the injection is administered
intra-muscularly). Other allergens
identified in children mainly concern ingredients of pharmaceutical products
and cosmetics (sometimes as a cause of “connubial” dermatitis), rubber
derivatives, which are often responsible for shoe dermatitis, resins, and
plants. Certain occupational allergens
(hairdressing, construction, metal work) are, of course, only found in
adolescents.
Correlation
between the localization of the lesions and the nature of the allergens.
cosmetics [e.g. methyl-(chloro)isothiazolinone];
perfume components;
plants
Peri-orbital area: ophthalmic preparations;
nickel, cobalt
nickel, cobalt, and palladium;
flavoring agents (cinnamic aldehyde)
Ears: nickel
and cobalt;
ear drops
Trunk: clothing
dyes;
rubber additives;
nickel (peri-umbilically)
Arms: cosmetics
(e.g. sunscreens);
aluminum (vaccines);
plants
Wrists: nickel
and cobalt;
dichromate (leather watch-strip)
Hands and fingers: preservative agents
(cosmetics, play gels, plasticine);
nickel and cobalt;
plants;
rubber and resin components
Nates and thighs: aluminum (vaccines)
Diaper area: topical
pharmaceutical (e.g. ethylenediamine, neomycin);
cosmetic products
Legs: plants;
orthopedic appliances [resins (PTBP), epoxy]
Feet: shoe
allergens (rubber additives, glues) (PTBP);
dichromate, plants, topical pharmaceutical products
Key words: children - allergens - atopy - patch
testing