Delayed-type hypersensitivity reactions allergic contact dermatitis

Dryness and irritation from a primary irritant such as BPO may limit therapy in some patients allergic contact dermatitis (delayed-type hypersensitivity reaction) has also been reported. ... 

Contact dermatitis is an allergic disease causing dry skin, redness and itching, which develops as a result of delayed-type hypersensitivity reaction. 

Allergic contact dermatitis is a delayed hypersensitivity reaction.30 Upon initial exposure, a substance penetrates the skin, binds to a protein and develops into sensitizing antigens. Subsequent exposures to that substance will then elicit an allergic reaction.25,29,30 Symptoms of allergic contact dermatitis are similar to those of the irritant type, but may take several hours to several days to develop following re-exposure.25,26... 

Type IV delayed hypersensitivity reactions are uncommon, but allergic contact dermatitis and localized erythema and blistering have been reported (SEDA-21,136). 

Maneb or mancozeb. Maneb and mancozeb have been found to cause allergic contact dermatitis, a delayed (type IV immune system response) hypersensitivity reaction. After sensitivity to a particular allergen develops, subsequent contact to minute doses of the antigen elicits an acute response. While allergic and irritant contact dermatitis usually have indistinguishable clinical characteristics, the former reaction is a true allergy whereas the latter reaction is one whose intensity is proportional to the dose applied (Rice and Cohen... 

The two types of contact dermatitis are irritant and allergic contact dermatitis, and they are clinically indistinguishable. Irritants involve a nonimmune response caused by the direct action of the irritant on the skin. Related, but different, is allergic contact dermatitis that is caused by a delayed hypersensitivity reaction of the immune system (see allergens below). Many chemicals have irritant properties and some examples are shown in Table 4.1.2.1. Dilute concentrations of corrosives can have... 

Contact urticaria usually clears spontaneously repeated exposure may produce dermatitis (eczema). In addition, it may be associated with allergic contact dermatitis (type-IV hypersensitivity), von Krogh and Maibach [4] tested 67 patients for immediate and delayed hypersensitivity, and 22 (33%) developed a positive delayed response subsequent to the initial wheal-and-flare reaction. The responsible agents were food products, rubber latex, cinnamic aldehyde, para-aminodiphenylamine, ethylaminobenzoate, ammonium persulfate, teak, epoxy resin and lemon perfume. They suggested that the term contact dermatitis of immediate and delayed type be used for patients exhibiting both types of reactions in the test situation, whether the initial reaction is uncharacteristic, urticarial or vesicular [4]. 

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