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ractitioner June 2014-258 (1772)27-31
Identifying the causes
of contact dermatitis
Damatology
en M Horn
Specialist in
of Edinburgh,
causes of contact
dermatitis?
CONTACT DERMATiTiS
RESULTS FROM SKIN
CONTACT WITH AN
EXOGENOUS SUBSTANCE
It can be caused by directskincontact,
airborne particles, vapours or light.
Individuals of any agecanbe affected.
The condition can lead to disability and
unemployment andis animportant
occupational problem.
VARIANTS
Thetwo most com mon variants are
irritant contact d ermatitis (ICD) and
allergic contact d ermatitis (ACD).
ICD is more com mo n andhas aworse
diagnosis
be confirmed?
prognosis. Studies of unselected
populations suggest that the
prevalence ofACD isbetween
7 and13 .
Otherlesscomm on forms of contact
dermatitis include photocontact allergy
and,in food handlers, protein co ntact
dermatitis.^
Often m ultiple mechanisms are
involved. For example, an underlying
endogenous eczema or impaired skin
barrier predisposes toICDwhich in turn
facilitates penetration of potential
allergens.
are the
management
options?
irritant contact dermatitis
ICDis aform of eczema and is induced
by direct inflamm atory pathways
witho ut prior sensitisation. Strong
irritants or caustic agentscancause
acute changes bu t more often ICD is
chronic and caused by repetitive
exposure to m ultiple weaker irritants.
These may be eitherwet,such
as
water
soaps, detergents, solvents, weak acids
or alkalis, ordry,such
as
friction, low
humidityandheat orcold.
Ailergic contact dermatitis
Classical ACD is mediated by typ e 4
cell-mediated imm unity. Sensitisation
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T h e Prac t it ioner
June 2014-258 (1772)27-31
SPECIAL REPORT
CONTACT DERMATITIS
FIGURE
(LEFT)
Sensitisation phase
of allergic conta ct
dermatitis
FIGURE 2 (RIGH T)
Elicitation phase of
allergic con tact
dermatitis
Hapten
Allergen is
formed by
hapten-peptide
binding
/-i*r
Epidermal and
dermal de ntritic
cells
Antige n complex is
transported to regional
lymph nodes by activated
den tritic cells
Hapten-specific
. , T cells form
(O) (O) and proliferate
I T ^ ^
Hapten
Lymph node
Releaseof
inflammatory
mediators
occurs within 5 to 6days of skin
contact with
a
p otential allergen but at
this first exposure thereisno
inflammation,seefigure1,above.
On re-exposure previously sensitised
T cells recognise the antigen and a
cascade of events occurs resulting in
inflammation 2to 72 hourslater see
figure2,above.
Metabolism ofasubstance may be
necessary to allow it to penetrate the
stratum corneum and further
metabolism may be required within the
epidermis before immunological
stimulation can
occur.
Mutations o f
genes encoding enzymes and
cytokines involved
in
these processes
influence individual susceptibility t o
ACD. Frequent exposure
and
high
concentrations of potential allergens
increase the risk of sensitisation.
Some sensitisers, suchassunscreen
ingredients may only becom e capable
of inducing ACD after they are exposed
to ultraviolet light. Most can also induce
classical ACD .
If eczema is recurrent/persistent, or
occurs
in
an individual with no previous
history of eczema, contac t derm atitis
should be
considered,
seefigure 3,
opposite. As in any eczema, contact
dermatitisisitchy. If acute there will be
erythema, oedema, vesicles, and
exudation.If theconditionischronic,
the skin will be iichenified with scaling
and fissures.
The distribution of
an
eruption may
provide valuable diagnostic clues.
Dorsal aspects of
the
hands
are
the site
most often affected byICD,usually w ith
involvement ofthefinger websaswell,
see
figure
4,
opposite.
ACD caused by shampoo ingredients
typically involves the face and uppe r
trunk, usually sparing the scalp. Hair
dyes can elicit intense inflammation
resembling angioedema but scaling or
flaking during resolution indicates an
eczematous process.
An occupational factorshouldbe
sought if eczema deteriorates d uring
the working w eek and improves at
weekends or during periods of leave.
Protein contact dermatitis
individuals suffering from protein
contac t derm atitis develop vesicles
within minutes at sites of
skin
contact
with raw meat,
fish,
enzymes or plant
proteins. Improvement occurs within a
few hours but with repeated exposure
chronic eczema can evolve.
Inflammation
is
usually confined to
Com mon causes of allergic contact d ermatitis
Allergen
Nickel
Fragrances
Biocides including m ethylisothiazolinone *
Rubber additives (thiurams,
mercaptobenzothiazole and carbamates)
Potassium dichromate
p phenylenedi mine
Plants (sesquiterpene lactones) *
Colophony *
Topical antibiotics an d corticosteroids
Acrylates
Epoxy resins
Sunscreen ingredients
Sources of exposure
Metal jewellery, buckles, studs on cloth ing, coins
Cosm etics, toiletries, wet wipes, room fresheners, fabric c ondition ers,
household produ cts, scented candles, incense sticks, aromatherapy oils
Cosmetics, toiletries, wet wipes, fabric conditioners, household
products, pharmaceutical creams, industrial oils and cooling fluids,
water-based paints
Natural and synthetic rubber gloves and other rubber articles
Tanned leather, ceme nt
Permanent and sem i-permanent hair dyes
Compositae species, tulips and m any others
Adhesive in fabric dressings,rosin,solder pine trees
Pharmaceutical creams and ointments
Artificia l nails
Adhesive systems
Sunscreens, cosmetics, toiletries
Can also cause
airborne contact dermatitis $
Can also cause
ph otocontact allergy
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c co ntact de rmatitis caused by flavouring agents
ICD.Patch testing is required
reaks indicate that this bullous erup tion was cau sed
is eczema. Patch testing is indicate d
the hands andisoften ofsuchseverity
thatachange of occupation may be
necessary. The mechanism of pro tein
contact dermatitis
is
po orly understood.^
COM MON CULPRITS
Irritants
Cumulative effects of
water
soaps and
detergents are the most co mm on cause
ofICDw hich affects the hands more
often than any other site. Frequent hand
washing associated with thearrivalofa
new babyisoften responsible for new
onset hand eczema
in a
young mother.
ICDiscommoninoccupations
involving frequent hand washing such
as hairdressing, he althcare, and
catering.
Because of their im paired skin
barrier func tion atopic individuals
workinginthese occupations are at
especially high risk.
If eczema
is
recurrent,
persistent,or
occurs in
patient
withnoprevious
history of eczema,
contact demratitis
should
be
considered*
Sweatandcaustic substances
trapped next to the
skin
by waterpro of
gloves or pro tective clothing can all
cause
ICD.
Incontinent patients are at
risk of developing
ICD
of the perineum.
Cosmetics often contain abrasive
particles capable of ind ucing ICD.
Airborne irritants include abrasive dusts,
especially dry cem ent,aswellascaustic
vapours. Organic solvents, acids and
alkalis, low hu midity, heat
and
cold are
also im portant causes ofICD.
Allergens
Nickei,
fragrances, rubber accelerators
and biocides are the most comm on
sensitisers,seetable1,p28 . Biocides are
added to products to prevent growth of
pathogens. M ethylisothiazolinone, a
biocide , is responsible foracurrent
epidemic of CDinvolving numerous
well known brands of cosmetics and
toiletries. Sensitised individuals entering
rooms freshly decorated wit h
water-based paints containing
methylisothiazolinone can develop
airborne ACD on exposedskin.
More comm on causes of airborne
ACD include fragrances in room
fresheners, scented candles or incense
sticks. Seasonal eczema on exposed
skin suggests allergy to plants, see
figure 5 below left. Acrylate vapours
released during application or sculpting
of
artificial
nails are
an
increasingly
com mo n cause of airborne ACD
eczema in beauticiansandtheir clients.
Patients with leg ulcersandstasis
eczema are at especially high risk of
developing allergies to ingredients of
their topical treatments, dressings and
bandages,seefigure 6, below left.
It
is
important to remember that
topical antibiotics and corticosteroids
can cause
ACD.
SIGN guidelines
recomm end that bandages and
compression hosiery should be latex
free to avoid inducing allergy to rubber
accelerators.^
Carers applying topical treatments to
individuals already sensitised to these
chemicals should wear accelerator-free
gloves. Wool alcohols lanolin) and
parabens, once common sensitisers in
leg ulcer patients, have becom e
infrequen t causes of CDnow that
they are seldom found in dressings and
bandages.
Inth e
UK,
sunscreen ingredients are
the m ost frequent cause of
photoc ontact allergy bu t in sunnier
latitudes allergy to topical NSAIDs in
sports gelsis anincreasingly com mon
problem. Itcanbe difficult to
differentiate between photocontact
allergy, photosensitivity
and
airborne
ACD,seefigure7
p30.
Involvement of
the posterior auricularareassuggests
that eczema atanexpose d site is
caused byanairborne substance, not
light,
see
figure
8,
p30.
If relevant allergenscanbe identified
thereis arealistic prospect o f cure.
INVESTIGATIONS
A careful history
is
impo rtant, enquiring
about exposure at workandat home,
hobbies, cosmeticsandtoiletries and
timing of the eruption.
Ageshouldnot
be deterrent
top tchtesting*
If
CD is
suspected the patient
should be referred to secondary care
for patch
testing.
Age should not bea
deterre nt to p atch testing. This involves
applying standardised concentrations
of suspected substances to theskin
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.T he Practi t ioner Jun e 2014-2 58 1772)27-31
SPECIAL REPORT
CONTACT DERMATITIS
FIGURE 7 LEFT)
Exposedsite
eczema,
Photosensitivity or
contact dermatitis?
FIGURE RIGHT)
Posterior auricular
involvement
suggests airborne
contact dermatitis,
in this case dueto
an
epoxy
resin in a
floor layingadhesive
under occlusion leaving them in place
for 48 hours, see figure 9, below.
Readingsare takenon removal of the
patches
and
two dayslater It takes
expertise to select allergensandto
interpre t results.
Photopatch testing,usetests and
repeated open application tests may
also be appropriate for some patients.
MANAGEMENT
Accurate diagnosis, avoidance of
identified allergens and prote ction from
irritants are the key to successful
treatment,
see
table2,below.
Patient information leaflets are
available from the B ritish Association of
Dermatologists, see Useful information
box,
p31.
Formal hand dressings may be
FIGURE 9
Patch testing :
standardised
concentrations of
suspected culprits
are applied to
the skin under
occlusion and
left for 48 hours
necessary ifhandeczemaissevere.
Cotton gloves or dressings can be
covered by waterproof gloves during
unavoidable we t tasks. At hom e PVC
gloves areasafer choicethanrubber or
nitrile
as
sensitisers in rubber can
penetrate co tton gloves or dressings.
Inan occupational setting glove
choice will depend o n the nature of the
chemicals involved.
Topical steroids of sufficient potency
should be prescribed
as
ointments not
creams. The latterare lessemollient
than ointments and contain p otentially
sensitising excipients usually n ot
presentinthe equivalent ointment.
Manage ment of allergic contact
dermatitis
Identifyandavoid the cause
Protect affected skin
Prescribe cotto n gloves for hand
eczema
Use
soap substitutes at hom e and
at work
App ly emollients frequently at home
and at work
Usetopical steroid ointmen ts not
creams)
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points
Wrexham and Associa te GP Dean for N orth Wales
dermatitis results fromskincontact with an
It canbecausedby direct contact,
light.
Individuais otan y ag e
ected. The tw o most co mm on variantsareirritant
andallergic contact de rmatitis
ICD
is
m ore comm on and
has a
worse prognosis.
lesscom mo n forms of contact dermatitis include
ntact allergy
and,in
food handlers, protein con tact
Disa form of eczema and isinduced by direct
pathways witho ut prior sensitisation.
sical ACD is mediate d by typ e 4 ce ll-mediate d
unity. Sensitisation occurs within 5 to 6days of skin
tact w ith a potential allergen but at this first exposure
no inflamm ation. Frequent exposure and high
ntrations o f poten tial allergens increase the risk
sensitisation.
eczem aisrecu rrent/persistent, o r occursinan
atitis should b e considered. Dorsal aspects of the
re most often affecte d by
ICD,
usually wit h
webs.
Cumulative effects of
soaps and detergents are the most co mm on cause
which affects the hands m ore often than any
site.
fragrances, rubber acceleratorsandbiocides are
ost co m m on sensitisers in ACD. Patients wi th leg
ecze ma are at especially h igh risk
eloping allergies to ingredients of their topica l
Inthe UK, sunscreen
ents are the most frequent cause of ph otocon tact
t in sunnier latitudes allergy to topical NSAIDs
sports gels is an increasingly com m on p roble m.
CD issuspected the patient should be referred to
t be a
nt to patch testing . Accu rate diagnosis, avoidance
ens and prote ction f rom irritants are
ul treatm ent.
ds of sufficient potency
should
be
as ointm ents not creams. The latter are less
tain potentially
sing excipients usually no t present in the equivalent
ent. Patients with eczem a that is in an unusual
ment should be referred to secondary care for
Ingredient lists of prescribed topical
treatments should be checked to
ensure that previously identified
allergens are not inadvertently supplied
to the patient.
If contact
dermatitis
persists
a change of
occupation
m a y b e
necessary
Patients with eczema tha tisin an
unusual distribution, recurrent or
persistent despite appropriate
managem ent should be referred to
secondary care for investigation and
intensive treatment. Patch testing is
especially impo rtant for patients
suffering from chronic hand eczema,
facial orstasiseczema.
Treatments available in secondary
care include phototherapy, alitretinoin
for refractoryhandeczema, azathioprine
and ciclosporin. If contact derma titis
persistsachange of occupation may
be necessary.
REFERENCES
Bourke
J,
Coulson
I.
Englisin
J.
Guidelines for the
manageme nt of contact dermatitis: an update. rJ
Dermato/2009;160(5):946-954
2 Hjorth N, Roed-Petersen
J.
Occupational protein
contact derm atitis in food handlers.Contact Dermatitis
1976;20):28-42
3 Scottish Intercollegiate Guidelines Network. SIGN 120.
Management of chronic venous teg ulcers. SIGN.
Edinburgh. 2010
4 RuzickaT Lynde CW, Jemec GBE et
al.
Efficacy an d
safety oforalalitretinoin C9-cis retinoic acid) in patients
with severe chronic hand eczema refractory to topic ai
corticosteroids: results ofarandomized, doube-blind.
placebo-controlled, multicentre trial. rJ Dermatoi
2008;158(4):808-817
Useful inform ation
British Association of Dermatologists
Patient informa tion leaflets on hand
dermatitis and contact d ermatitis
www.bad.org.uk
National Eczema Society
www.eczema.org
W e welcome your feedback
If you wouldliketo comment onthis
article or
have a
question for t he
authors, write to :
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C o p y r i g h t o f P r a c t i t i o n e r i s t h e p r o p e r t y o f P r a c t i t i o n e r M e d i c a l P u b l i s h i n g L t d . a n d i t s
c o n t e n t m a y n o t b e c o p i e d o r e m a i l e d t o m u l t i p l e s i t e s o r p o s t e d t o a l i s t s e r v w i t h o u t t h e
c o p y r i g h t h o l d e r ' s e x p r e s s w r i t t e n p e r m i s s i o n . H o w e v e r , u s e r s m a y p r i n t , d o w n l o a d , o r e m a i l
a r t i c l e s f o r i n d i v i d u a l u s e .
