Irritant Contact Dermatitis or ICD is a localized skin inflammation
caused exogenously; that is, it is the result of direct contact of the
skin with external irritants. The immune system plays no part in the
development of ICD. The skin irritation is the result of a local skin
response to the irritant.
The irritants, which cause irritant contact dermatitis, include a wide
variety of organic and inorganic chemicals and substances, metals, environmental
factors and physical factors. Acids and alkalis are the most common
Classes of irritants
Acids: Various types of acids act as corrosive irritants on the skin
and produce, more or less, the same clinical features, such as, erythema,
vesication and tissue necrosis. Hydrofluoric and sulfuric acids cause
the severest reactions, even at low concentrations.
Hydrofluoric acid is used in the semi-conductor, glass, metal, and
stone industry and is the only substance which dissolves silicon. It
is also used in households to remove rust and metal stains. A hydrofluoric
acid skin reaction can be very painful, since it can penetrate deep
into the skin and cause tissue and even bone damage. At low concentrations,
the onset may be delayed for a day, but the effect can be just as painful,
as it slowly penetrates the skin.
Sulfuric acid is widely used in numerous industries, such as, fertilizers,
textile, pigment, explosives and paper, to name a few. Most at risk
are jewelers, electroplaters, metal cleaners and storage battery makers.
Chromic acid, used in chrome plating and copper stripping can perforate
the nasal septum, and nitric acid, used as rocket fuel and in laboratories,
can be very corrosive.
Organic acids are, generally, less irritating than inorganic acids.
Acetic, acrylic, formic and salicylic are the common irritants, when
there is prolonged exposure to them. Formic acid, used in leather and
natural latex manufacture, has the highest corrosive power of the organic
Alkalis: Alkalis often cause more damage than acids, excepting hydrofluoric
acids. Clinical features in alkali exposure generally do not show vesicles,
but rather a necrotic skin, which is initially dark brown, then black
and finally hard, dry and cracked. Alkalis disturb the skin barrier,
denature proteins and act on fatty acids to produce soaps, which facilitate
more alkali penetration deep into the skin. Some strong alkalis are
sodium and potassium hydroxides and carbonate, used in bleaching, dyeing,
soaps and detergents.
Cement mixed with water releases the highly alkaline calcium hydroxide,
which can cause severe ulceration. The reactions appear 10 to 12 hours
after exposure. Chronic irritant contact dermatitis due to repeated
exposure to cement may develop over months. In cement workers, hands
and lower limbs are usually affected.
Metal salts: Many salts produce clinical features, ranging from ulceration
to folliculitis and pigmentary changes. Arsenic salts produce persistent
folliculitis and sometimes a systemic toxicity. Widespread preventive
measures are needed against arsenic, which is used in pesticide production,
semiconductor and smelting industries. Cobalt salts can cause both irritant
and allergic contact dermatitis. Mercuric salts, once popular disinfectants,
are mostly no longer used due to risks of sensitization and their general
toxicity. However, mercuric salts can be found in waste from the gold
industry where the metal is used to extract gold from crushed rock.
Solvents: Many types of solvents are used in chemical reactions, metal
refining and dry cleaning and nearly all cause skin irritation of varying
degrees, with turpentine also causing allergic sensitization. Solvents
act by impairing the skin barrier, thus increasing absorption by the
skin of chemicals. Prolonged exposure can cause severe burns, systemic
symptoms and sometimes even death. Repeated exposure causes erythema,
scaling, dryness and eventually eczema. Coal tar solvents can cause
drying and defatting from vapors alone. Ethers, esters and ketones are
all irritants to different degrees.
Alcohols: Alcohols, used widely as solvents, preservatives and disinfectants
in the cosmetic industry, are mild irritants, but prolonged exposure
may cause irritation and toxicity. The intensity of such reactions depends
on the number of carbon atoms of the alcohol. Alcohol, it is theorized,
acts by disrupting the skin barrier.
Detergents and cleansers: Skin cleansers rarely cause irritant contact
dermatitis, except when the skin is damaged. Detergents are a common
irritant present in cleansers, cosmetics and household cleaning products.
They work by impairing the skin barrier. Anionic detergents, such as,
alkyl sulfates and alkyl carboxylate salts are more irritating than
the ionic and amphoteric ones.
Disinfectants: Disinfectants are weak irritants and cause chronic irritant
contact dermatitis due to cumulative doses. Disinfectants can be alcohols,
aldehydes, phenol compounds, halogenated compounds and dyes, among others.
Ethylene oxide, used for sterilization, can be a cause of burns among
hospital staff. Aldehydes are more irritating than alcohols. Formaldehyde
is a common sensitizer even at low concentrations because of its high
chemical reactivity with proteins. Chlorine compounds, used as disinfectant,
can cause skin irritation, particularly at higher temperatures.
Food: Ingredients in some foods result in some people working in agriculture,
catering and food processing industries, to suffer from chronic irritant
contact dermatitis. Such a condition is accepted as normal and medical
advice is rarely sought. See elsewhere on this web site for common food
allergens which can also work as irritants with repeated skin contact.