Contact dermatitis

Dermatitis (inflammation of the skin), is a common problem which affects most people at some time. It usually results in red, swollen or blistered, intensely itchy areas of skin.

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

But many others will experience contact dermatitis, also known as exogenous dermatitis, (meaning dermatitis from external factors). Contact dermatitis is the result of direct contact with a trigger substance, such as a single chemical or a product such as detergent.

Types of contact dermatitis

There are 2 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 the 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; and
  • motor mechanics.

Allergic contact dermatitis

The allergic form of contact dermatitis is less common, affecting a small number of people who 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 to the skin. Costume jewellery, watch bands, metal studs on jeans or sleepers in pierced ears are usually to blame.

Other allergens (triggers for allergy) are chromates (especially in cement), rubber (latex), rosin (present in many adhesive plasters), hair dyes, and some creams and ointments used for medical purposes.

Occasionally people might develop 'photocontact dermatitis', in which a rash develops in areas that have both contacted the allergen and been exposed to sunlight. Sunscreen and antibacterial soap can produce this effect.

What to do when you have contact dermatitis

When contact dermatitis is suspected, the obvious first step is to try to find the cause. With an irritant cause this is usually easy, as the dermatitis is often confined to those areas 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 and poison ivy are common causes.

Sometimes patch testing, in which a number of suspected materials are applied by a doctor to separate areas of skin for up to 48 hours, will solve the mystery.

Treatment of contact dermatitis

Treatment of contact dermatitis usually involves applying emollients such as sorbolene or emulsifying ointment. Corticosteroid creams or ointments may also be necessary — generally these should be used just for a short period. Antihistamines or oral corticosteroids may also be prescribed. If secondary infection is present, antibiotics may be needed.

Self-care remedies which may help soothe your skin include applying cool wet compresses, bathing in cool water with baking soda or colloidal oatmeal and using anti-itch lotions such as calamine.

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.

Prevention of contact dermatitis

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

  • Use a mild non-fragranced skin cleanser rather than soap.
  • Dry your hands well after washing.
  • Apply moisturiser liberally, several times a day.
  • Protect the hands with gloves, but avoid sweating.
  • Barrier creams may provide some protection for people working with dyes and chemicals, although their effectiveness has not been proven.
Last Reviewed: 26 November 2012
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References

1. Contact Dermatitis. [revised Feb 2009]. In: eTG complete [Internet]. Melbourne: Therapeutic Guidelines Limited; 2012 Nov. http;//online.tg.org.au/complete/ (Accessed Nov 2012).
2. DermNet NZ [Website] www.dermnetnz.org (Accessed Dec 2012).
3. Mayo Clinic. Contact dermatitis. [Website]. July 2011. http://www.mayoclinic.com/health/contact-dermatitis/DS00985 (Accessed Dec 2012).
4. Bauer A. et al. Treatments to prevent irritant hand dermatitis in the workplace. [Internet]. Cochrane Database of Systematic Reviews 2010. Issue 6. Art No: CD004414. DOI (Accessed Dec 2012).
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