The clinical presentation of irritant contact dermatitis or ICD depends on the properties of the triggering agent, the individual, and environmental factors.

The environmental factors include mechanical pressure, concentration, temperature, humidity, pH and length of contact with the agent. Low water content and cold dry up the skin, making penetration easier for the irritants. Cold alone can bring about this condition by cracking the skin. Occlusion and excessive humidity increase the water content of the skin, resulting in increased absorption of water soluble substances. Moreover, the irritated skin may become more susceptible to superimposed allergen sensitization.

The important characteristics of individuals that influence clinical development are age, race, sex, inflammation site, preexisting skin condition and sebaceous activity. Infant and older people have severer clinical responses due to their less robust skin. Caucasians are more susceptible to irritant contact dermatitis than Black African – African-Americans. Though Asian people often claim high sensitivity to irritants, the frequency of actual sensitivity is about the same as in Caucasians. Compared to men, the upper extremities in women are more often affected. Genetic factors also play a role, as do atopic diseases, which increase the chances of individuals developing irritant contact dermatitis. Lastly, hands and face are the most common sites affected, due to excessive exposure to water, soaps and detergents, especially in women.

Clinical features of various type of irritant contact dermatitis

Acute irritant contact dermatitis: Commonly an occupational disease, acute irritant contact dermatitis develops lesions restricted to areas contacted. These regions have sharply demarcated borders. The inflammation peaks quickly in minutes or hours and then starts healing. This phenomenon is called decrescendo. Signs include erythema, edema and bullae and symptoms include burning, stinging and soreness at the affected site. Common irritants are acids and alkalis.

Acute delayed irritant contact dermatitis: In acute delayed irritant contact dermatitis, the response is seen 8 to 24 hours after first exposure and thus may mimic allergic contact dermatitis. But the symptoms are usually burning and not pruritus. There is hypersensitivity to water and touch. Common irritants are anthralin and ethylene oxide.

Irritant reaction irritant contact dermatitis: This type of irritant contact dermatitis occurs to people exposed to wet chemical environments and include hairdressers, caterers and metalworkers. It is characterized by one or more of signs, such as, scaling, redness, vesicles, pustules and erosions. This condition is often observed under occlusive jewellery, spreading from the fingers to the hands and forearms.

Cumulative irritant contact dermatitis: Cumulative irritant contact dermatitis occurs due to multiple injuries to the skin sub-surface in close succession, without sufficient time for the skin barrier function to heal. It can be caused by multiple stimuli or by repeated actions of the same stimulus. Symptoms appear when the cumulative damage exceeds a threshold, specific to the individual. Clinical features also depend on the properties of the irritants, such as, pH, solubility, detergent action and physical state. Common signs are lichenification and hyperkeratosis and less common ones could be erythema and vesicles.

Traumatic irritant contact dermatitis: Traumatic irritant contact dermatitis occurs after injuries to the skin, such as, burns, lacerations and acute irritant contact dermatitis. Eczematous lesions are a feature of this condition. Cleaning by strong soaps and detergents can also be a cause. It occurs mostly on the hands. There is redness, scaling and cracks on the affected areas. It is a persistent disease and healing can take more than 6 weeks.

Pustular and acneiform irritant contact dermatitis: This type of irritant contact dermatitis is the result of exposure to metals, minerals, oils, tars, greases and naphthalene. In pustular and acneiform irritant contact dermatitis the lesions develop outside of typical acne, particularly in patients with atopic dermatitis and seborrhea.

Subjective or sensory irritant contact dermatitis: Subjective or sensory irritant contact dermatitis is marked by reports of burning and stinging without any visible signs of inflammation. Known irritants are lactic and sorbic acids.

Airborne irritant contact dermatitis: Airborne irritant contact dermatitis affects the sensitive skin of the face and the region around the eye. The clinical features appear to mimic photo allergic reactions which, however, can be identified by the involvement of the upper eyelids, philtrum and submental regions.

Frictional irritant contact dermatitis: Frictional irritant contact dermatitis results due to repeated low-grade frictional trauma. It often plays a role in the development of allergic contact dermatitis and irritant contact dermatitis. Frictional irritant contact dermatitis often leads to progressive hardening, thickening and toughening of the affected region.

Pathological presentation of irritant contact dermatitis

The pathologic features of irritant contact dermatitis include a wide variety of inflammations, necrosis of epidermal keratinocytes and mild spongiosis. The combination of an upper dermal perivascular infiltrate of lymphocytes with minimal extension of inflammatory cells into the overlying epidermis and widely scattered necrotic keratinocytes is most typical. True features of interface dermatitis are absent and spongiosis should be focal or absent. Over time new pathologic features, such as, acanthosis with mild hypergranulosis and hyperkeratosis appear. In aggregate, these elements are not specific and they cannot be distinguished with certainty from chronic allergic contact dermatitis or other cause of eczematous contact dermatitis.