History and exam
Key diagnostic factors
common
occupational history of exposure
history of atopic dermatitis
People with atopic dermatitis are at equal risk of developing contact dermatitis (and higher risk of developing contact dermatitis to weaker allergens) compared with people without contact dermatitis.[27]
Consider patch testing atopic dermatitis patients when allergic contact dermatitis is suspected.[28]
previous episodes of similar dermatitis
A history of previous episodes of allergic contact dermatitis suggests a prior sensitisation. Symptoms may occur earlier on repeat exposure. If an allergen is identified from prior episodes of contact dermatitis, subsequent episodes of contact dermatitis may be because of unrecognised exposure to the same allergen or exposure to a cross-reacting allergen.
acute onset
Irritant contact dermatitis occurs within minutes to hours of exposure to a severe irritant and within days to weeks of exposure to a mild irritant.
Allergic contact dermatitis typically occurs within 24 to 72 hours of exposure in a previously sensitised individual.
affecting hands and face
Irritant contact dermatitis most commonly occurs on the hands and face.
In irritant contact hand dermatitis, the dominant hand is more severely affected. Thicker-skinned areas, such as the scalp, palms, and soles, can be spared despite contact with the allergen.
Eyelids are commonly affected areas on the face due to the thin skin. This is true for both allergic and irritant contact dermatitis.
affecting sun-exposed skin
Phototoxic or photoallergic dermatitis presents on the sun-exposed areas of the face, upper chest, and forearms.
sparing of non-exposed areas of skin
Airborne allergens or irritants cause eruptions on the head, neck, chest, and arms with sparing of clothed areas similar to photoallergic contact dermatitis.
pruritus
More common in ACD than ICD.
burning
More common in ICD than ACD.
erythema
Equally common in ACD and ICD.
vesicles and bullae
More common in ACD than ICD, though may occur in severe ICD.
uncommon
urticaria
Allergic contact urticaria can occur with exposure to protein allergens such as latex rubber, as well as certain types of foods upon cutaneous contact.[29]
Substances capable of causing non-immunological contact urticaria that are seen occupationally include cobalt and platinum salts and balsams.[30][31]
lichenoid lesions
Common with allergic contact dermatitis to metals and tattoo pigments.
corrosion or ulceration
Occurs in irritant contact dermatitis to severe irritants such as alkalis, acids, solvents, and gases.
pustules and acneiform lesions
Occurs in irritant contact dermatitis to oils, greases, arsenic, and chlorinated naphthalenes.
Other diagnostic factors
common
scaling
More common in chronic contact dermatitis.
lichenification
More common in chronic contact dermatitis.
social history of exposure
Some recreational activities, such as those that involve frequent exposure to water, can lead to higher risk of contact dermatitis. Occupations requiring use of cosmetics or personal preference for frequent use of cosmetics can lead to increased risk of irritant facial dermatitis.
persistence of symptoms
Symptoms of allergic contact dermatitis can resolve within a few days after exposure, so persistence of symptoms indicates continued exposure, and may help to identify the allergen.
Symptoms of irritant contact dermatitis often improve after 3 to 6 weeks away from the irritant.[9]
uncommon
crusting
May suggest secondary impetiginisation.
erythema multiforme
Occurs mostly with allergic contact dermatitis to exotic woods.
cellulitic lesions
Can occur in allergic contact dermatitis to formaldehyde, gold, neomycin, or nickel.
leukoderma
Can occur in allergic contact dermatitis to paraphenylenediamine.
hypopigmentation/depigmentation
Can occur in allergic contact dermatitis to paraphenylenediamine, adhesives, and rubber accelerators.
hyperpigmentation
Occurs especially in irritant contact dermatitis to phototoxic agents and radiation, or allergic contact dermatitis to metals. [Figure caption and citation for the preceding image starts]: Allergic contact dermatitis to nickel in earringFrom the personal collection of Dr Snehal Desai [Citation ends].
purpura
Can occur in allergic contact dermatitis to black rubber or irritant contact dermatitis to fibreglass.
miliaria
Occurs in irritant contact dermatitis to occlusive clothing, adhesive tape, and aluminium chloride.
alopecia
Occurs in irritant contact dermatitis to borax and chloroprene dimers.
granulomatous lesions
Occur in irritant contact dermatitis to beryllium, silica, and keratin.
Risk factors
strong
occupation with frequent exposure to water or caustic material
Water exposure and microtrauma at work increase the risk of developing contact dermatitis; a compromised epidermal barrier allows easier penetration of irritants and allergens. People at risk include labourers, food-industry workers, machine operators, farmers, healthcare professionals, janitors, dry cleaners, cooks, florists, beauticians, and hairdressers.[3][9]
atopic dermatitis
Patients with atopic dermatitis (atopic eczema) have an increased risk of developing irritant contact dermatitis on the hands and an increased risk of occupational contact dermatitis, with a worse prognosis. The increased susceptibility to irritants may be due to a compromised skin barrier. Allergic contact dermatitis (ACD) does not, however, appear to be more common in atopic people, except for ACD to metals.[9][18]
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