Contact dermatitis is a skin disease that occurs due to exposure to external
irritants or allergens. Also known as contact eczema, it is marked by
a characteristic itchy (pruritic), rough, scaly (in well-defined plaques),
reddened and inflamed skin condition.
Types of contact dermatitis
Irritant contact dermatitis (ICD): Around 80% of all contact dermatitis
conditions are of this type. ICD is caused when the skin comes in contact
with some toxic substance generally in the form of irritant chemicals
found in soaps, solvents, acids, or alkalis. This apart, these chemicals
can also be found in personal care preparations, plants, topical applications,
home made therapies or chemicals one is exposed to in certain occupations.
Allergic contact dermatitis (ACD): ACD makes up the rest of the 20% of
contact dermatitis cases. ACD is a late-onset hypersensitivity of the
skin when it is exposed to chemicals to which a patient has been intolerant
for some time.
The kind of reaction of the skin in the case of ACD and ICD is determined
by the causative chemical, the extent and nature of exposure, and the
individual patient’s sensitivity. However, one must be cautious
while distinguishing between ICD and ACD, since they have almost identical
clinical features particularly in the chronic condition.
Apart from ICD and ACD, there are two other variants of atopic dermatitis
Systemic contact dermatitis: This occurs when a patient with a history
of contact allergy becomes exposed to an irritant chemical through a systemic
means, for example an injection, oral, intravenous, or intranasal application.
Airborne contact Dermatitis: This is caused by airborne allergens (mainly
from plants, plastics, glues, rubbers, metals, insecticides, pesticides
etc) for example ragweed dermatitis that mainly occurs on the face.
Diagnosis and differential diagnosis of ACD
The best way to differentiate between ICD and ACD is a through a patch
test. Patch tests ascertain the type of allergen involved or an allergy
contact with the irritant agent.
Many patients often do not seek medical help especially in case of ACD
from obvious causes like jewelry, poison ivy, nickel, etc. However, in
many cases, easy identification of the cause and a clinical history is
not enough to determine the allergens and herein patch tests and skin
examinations are required. For instance, a patient who presumably suffers
from chronic hand dermatitis is unaware that it is actually being caused
by a personal care product.
Though patch testing is the mainstay of the clinical diagnostic procedure
in ACD, histology is also often necessary. This is also an integral part
of differential diagnosis especially to distinguish atopic dermatitis
from cutaneous T-cell lymphoma. The differential diagnosis of ACD must
also exclude other kinds of dermatitis such as ICD, stasis dermatitis,
seborrheic dermatitis, and acne rosacea. This apart, hand and foot ACD
must be differentiated from psoriasis and fungal infections.
In patients reporting widespread occurrence of the disease, it must also
be distinguished from other causes of erythroderma. But the diagnosis
is incomplete without a thorough knowledge of the clinical characteristics
of the condition. In case of ACD they are:
- Typical marked out itchy (pruritic), rough, inflamed (eczematous)
skin flares. These eruptions are sore and swollen in acute cases or
form of flaking plaques in chronic conditions.
- ACD eruptions are
characteristically restricted to skin locations that come in contact
with the irritant. However, one must be aware that
there is irregular or scattered distribution of the eruptions, depending
on the triggering allergen. For instance, liquid washes or shampoos
that the entire body is exposed to may result in more spread out eruptions.
- Urticaria, systemic reactions and photosensitive reactions are some
of the less prevalent occurrences.
From the pathological angle, in the acute phase of ACD there is a random
amount of skin spongiosis (spongy feeling to the skin due to increased
accumulation of fluid in the affected skin). In moderate to acute conditions,
distinct spongiosis leads to the formation of intraepidermal blisters
or vesicles. In the subacute to chronic stages, one can also see epidermal
hyperplasia and psoriasiform skin.
Any person of any age and any ethnicity can develop ACD. There are some
gender differences but it is mostly determined by the kind of exposure.
For instance, women are more prone to nickel allergy since they wear more
jewelry than men do. A person’s vocation also has a big role to
play in the development of ACD. In addition, prevalence of irritants can
differ according to geographical locations and climatic conditions. Again,
since preservatives have a major role to play in ACD, it may differ in
form in different places depending on the local official directives about
their use in personal care preparations.
The major 10 allergens recognized by the North American Contact Dermatitis
Group (NACDG) are:
- Nickel sulfate
- Neomycin sulfate
- Balsam of Peru (Myroxylon pereirae)
- Fragrance mix
- Sodium gold thiosulfate
- Cobalt chloride
- Bacitracin 13
The number one drug category that causes atopic dermatitis is corticosteroids.
Corticosteroids are anti-inflammatory medications that cause ACD in an
estimated 0.2% to 5.98% of people who use them. It is probably the number
one drug category for causing atopic dermatitis because the use of corticosteroids
is so widespread and common.
Treatment and Patient Counseling
Patient education form doctors should typically include the following
or something similar:
- Written details about the allergens and their effects .
- How to read
the labels of products so as to avoid exposure to irritants.
to identify and avoid allergens one is vulnerable to.
- How to trace
the allergens present in the surroundings, say for instance a spray
that your spouse uses and you are unknowingly allergic
Treatment of ACD involves:
- Identification of the causative allergens (primarily through patch
- Primarily application of topical corticosteroids and secondarily
- Avoiding the allergens after the course
of medication is over.