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Contact dermatitis is a condition in which the skin suffers inflammation, becoming red, itchy, swollen, and perhaps developing rashes, after coming into contact with a specific substance. It is known to be of two major types; irritant or allergic contact dermatitis.
This is quite common - it is more frequently encountered than the allergic type of contact dermatitis. It is a result of irritation and breach of the skin surface by a substance. For this reason, the nature and extent of the rash depend on how much of the irritant was present, and the duration of exposure.
This type of reaction shows no characteristic time lapse between exposure and the onset of dermatitis. Factors which may hasten the reaction or themselves act as irritants include exposure through wet skin, dry skin, and extreme climatic conditions.
Typical irritants include:
The rash or skin reaction is in response to skin irritation induced by the chemical.
This is a delayed or type IV hypersensitivity reaction carried out by T-lymphocytes in the epidermis. These cells come into contact with the antigen which has bound to the cell surface to form a new immunogen.
Sensitizing agents may include:
The contact between skin immune cells and specific antigens on the sensitizer provokes an immune-mediated or allergic reaction.
The reaction takes place in two phases, as is shown below:
These are a type of skin allergy in which the causative product causes a reaction only if the skin is concurrently exposed to ultraviolet or other forms of radiation present in sunlight. Some culprits include:
Allergic reactions are either acute (within 24-48 hours), or require some days or months to first manifest. Such reactions are typically very pruritic, papular, and ill-defined. The skin is reddened. Vesicular and oozing lesions may occur. Ulceration is rare. However, higher concentrations of some allergenic substances may give rise to irritant reactions as well.
Irritant contact dermatitis is more often associated with burning or stinging as well as, or instead of, itching. The skin may be fissured, as well as rough and dry. Redness, oozing lesions, and inflammation may develop with chronic irritant contact dermatitis. Pain may be present if the skin is cracked and cut, and the area is usually very tender.
Both forms of contact dermatitis are found on the parts of the body that are exposed to the causative agent. The hands, especially the interdigital webs, are thus a typical location. Eczematous lesions with oozing, papules, crusting, or thickening, are often present.
The following table summarizes some primary differences between the two types:
A careful history, with a physical examination, is supplemented with skin testing using the patch test if the reaction recurs frequently or persists for a long time. Treatment may vary from leaving the skin absolutely untreated, or washing it with copious amounts of water and avoiding further exposure to the offending substance, to corticosteroid therapy. Emollients are essential to lock in the skin oils and to keep the skin from scaling, helping the healing process. In most cases, the skin becomes clear within 3 weeks. Soap should not be used on affected areas.
Severe, persistent, or infected lesions may require systemic corticosteroids, antibiotics, or calcineurine inhibitors.