Contact dermatitis is an allergic or irritantinduced dermatitis arising from direct skin exposure to a substance.
Most common in children and adult women.
F > M
Exposure is most common in the home or industrially related.
Irritant contact dermatitis (80%) is caused by over-exposure to substances that cause damage to the skin. Once the epidermal barrier is damaged a secondary inflammatory response occurs. Irritants include soapy water, detergents, acid and alkaline solutions.
Allergic contact dermatitis (20%) occurs in sensitised individuals exposed to a specific low-molecular-weight chemical, such as nickel in jewellery, and components of hair dyes and perming solutions, perfumes, topical medicines and plants. Allergens are processed and presented by Langerhans’ cells in the skin causing a Th1 mediated type IV hypersensitivity response.
Contact dermatitis often affects the hands or face. Lesions may also affect the legs of patients with chronic venous insufficiency, when sensitivity to dressings is thought to be the cause. Lesions are erythematous itchy papules or blisters occasionally with oedema and fissures. Allergic contact dermatitis may be acute or chronic.
The allergens can be identified by patch testing and avoided. Where contact is unavoidable appropriate protection for the skin such as gloves should be used. For irritant contact dermatitis, topical steroids can be used. Use of aqueous cream instead of soap helps to reduce itching.