Irritant dermatitis is
different than allergic contact dermatitis. Irritant dermatitis is caused
by a substance applied for the first time or for a short period which can
cause cell damage if applied with certain concentration and for a
Many irritants cause
damage by exhausting the horney layer, denaturating keratin and altering
the water holding capacity leading to physio-chemical changes of the skin.
Repeated exposure with
the irritating substance which have an irritant must exceed a certain
threshold to cause an allergic reaction.
dermatitis is due to repeated exposure of the skin to a substance, which
can‘t at the beginning cause irritation or eczematization. Repeated
exposure with such substance may cause contact dermatitis.
dermatitis due to primary irritating factors is not an allergic reaction,
and must be differentiated from allergic contact dermatitis .
Primary irritants may
cause non-allergic inflammatory reaction on the first time the skin is
exposed to that specific substance. The severity of the reaction depends
on different factors, mainly the concentration of the substance , duration
of exposure and the local conditions of the skin.
dermatitis is common in infants and young children. Mild and simple
substances such as soaps and even saliva may cause irritation in infants
but may have no effect on older children .
irritants that may cause direct non-allergic reaction are:
Detergents , cosmetics
Plants , shrub, grasses
as in poison ivy , oak and others.
Metals : nickel,
dichromate in jewellary.
Fig. 173a.Primary irritant dermatitis (Metal)
Paraben: used in
cosmetics , creams and preservatives.
Antibiotics : neomycin.
Local anesthetics :
Antihistamine and even
topical corticusteroid preparations .
Colophony : in plasters
Balsam of Peru : in
perfumes and citrus fruits .
Fig. 173b.Primary irritant
Fig.173d. Primary irritant dermatitis(Stockings)
Wood alcohol : in
cosmetics , creams and lanolin ..
Rubber and plastic : in
clothing , shoes and gloves .
Alkalis: Such as soaps,
shampoos and detergents containing sodium, potassium, ammonium and calcium
hydroxides , which are used for the manufacture of detergents .
Plastic and other
Diapers are a common
cause of napkin dermatitis.
Toilet seats or plastic
pants of polyester may cause primary irritant dermatitis .
Acids : such as carbolic
acid ( phenol) may cause primary irritant dermatitis or even fatal toxic
effect especially in infants and young children .
Other acids as salicylic,
sulfuric, nitric, ionic, tannic may cause severe burn when it is
concentrated. Treatment of such cases is by immediate rinsing with water
and sodium bicarbonate or soap .
Gases and dust especially
in hot humid climate .
Insect repellents, air
fresheners, domestic pets as dogs, cats, birds, plants, roses and many
irritants causing contact dermatitis in different sites:
Scalp and face :
Hair dyes, hair spray, shampoos, and cosmetics .
fruits such as orange, lemon, apple coming in direct contact with the
skin, chewing gums and tooth paste .
Eyes : Mascara,
volatile gases, false eyelashes and cement .
Nails : Nail
Hands : Contact
with different irritants such as soaps, detergents, plastic gloves,
perfumes, orange, lemon juice and peel, onion, garlic and vegetable juices
coming in direct contact with the skin.
Crural and napkin
areas : Napkins, soaps, perfumes, topical preparations either powders,
medicaments or cosmetic preparations .
Trunk and abdomen :
Synthetics as wool , silk, polyester, dyes, chemicals perfumes or metals
in trousers and brassieres.
Lower limbs : Shoe
dermatitis due to leather , plastic or from dyes and chemicals used during
manufacture . Socks of wool or polyester or walking bare-footed especially
on the woolen and polyester rag or carpets may provoke irritant
The most common clinical
patterns of primary irritant dermatitis seen in the newborn are perianal
dermatitis and napkin dermatitis .
features of primary irritant dermatitis
dermatitis may present with acute erythema, swelling of the skin followed
usually by vesiculation and oozing. Crusted scaly surface develops in
Fig. 173f.Acute irritant dermatitis
In the chronic stage the
skin becomes thick, hyperpigmented and lichenified.
Fig.173g. Chronic dermatitis
Itching is the main
symptom of dermatitis and varies according to the irritant, stage, age and
the patient‘s threshold .
Secondary infection is
common due to excoriation by severe itching.
Patch test is sometimes
very helpful to spot the offending factor . It is important to note that
patch test should not be done in severe and extensive dermatitis until
controlling of the lesion especially in patients who are extremely
sensitive. Meanwhile, when doing patch-test care should be taken that the
patient is not under corticosteroids or antihistamine especially the long
acting ones, where these may lead to inaccurate interpretation .
Strong testing materials
in patch test should be diluted in order not to cause direct sensitization
or exacerbation of the primary lesions .
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