What is contact dermatitis?

Contact dermatitis is a type of dermatitis, or inflammation of the skin. Contact dermatitis can be caused by 'irritants' affecting the skin, such as detergents, while the 'allergic' form of contact dermatitis is due to sensitivity to substances, eg, nickel (which may be used in costume jewellery). Dermatitis can cause red, swollen or blistered, intensely itchy areas of skin.

Internal or external causes

Some people with an allergic tendency, often inherited, will suffer from the chronic form of dermatitis (atopic dermatitis) also known as eczema. This is sometimes referred to as "endogenous" (meaning from within) dermatitis.

But many others will experience a form of dermatitis called "exogenous", (or "contact") dermatitis. Exogenous means due to external factors. Contact dermatitis is the result of direct contact with a variety of substances.

Types of contact dermatitis

There are two types of contact dermatitis: irritant and allergic.

Irritant contact dermatitis

"Irritant" contact dermatitis is produced by the direct chemical effect of certain substances on the skin. The severity of the dermatitis will depend on how long the substance is in contact with the skin and the concentration of the offending material, as well as how susceptible the skin is.

Common causes of irritant contact dermatitis include detergents and solvents, acids, alkalis, oils and skin cleansers.

Certain occupations are more prone to this form of dermatitis. These include:

• homemakers
• caterers
• cleaners
• nurses
• builders
• hairdressers
• motor mechanics.

Allergic contact dermatitis

The "allergic" form of contact dermatitis is less common, affecting a small number of people who, for some reason, become sensitive to certain common everyday substances. They may have been in contact with these materials for years before the sensitivity develops.

The most common cause of allergic contact dermatitis, usually affecting women, is nickel. This is found in many metal objects worn next, or close, to the skin. Costume jewellery, metal studs on jeans or sleepers in pierced ears are usually to blame.

Other allergens (things causing allergy) are chromates (especially in cement), rubber and some creams and ointments used for medical purposes.

What to do when you have contact dermatitis

When contact dermatitis is suspected, the obvious first step is to try and find the cause. With an irritant cause this is usually easy, especially as the skin problem is often confined to those areas actually in direct contact with the irritant.

With an allergic cause the rash may be more widespread, making identification of the cause harder. If the rash is less obvious at weekends or during holidays, it is probably due to a work-related substance. A streaky rash is often due to an allergy to a plant which the affected person has brushed past. Primula, Rhus tree and chrysanthemum are examples of plants which can cause problems. Sometimes patch testing, in which a number of suspected materials are applied to separate areas of skin for up to 48 hours, will solve the mystery.

Treatment of contact dermatitis usually involves applying emollients or emulsifying ointment. Barrier creams and soap substitutes may be helpful. Corticosteroid creams or ointments may also be necessary - generally these should just be used for a short period. If secondary infection is present, antibiotics may be needed.

Aim to prevent contact

Whenever possible, contact with the cause of the dermatitis must stop. This might mean abandoning a favourite piece of jewellery, or taking meticulous care always to wear protective gloves when doing housework.

To prevent contact dermatitis on the hands, good skin care is important:

• use a mild skin cleanser rather than soap
• dry your hands well
• apply moisturiser liberally, several times a day.

Related topics

See also: Dermatitis - types of

Original material provided by myDr, 2007. Edited by everybody, February 2012.