Contact dermatitis is an inflammatory skin condition caused by skin contact with a chemical substance. The reaction can be non-immunological or imunnologically mediated and a wide range of different skin presentations have been described. The most common of these are eczema and urticaria but lichen planus, erythema multiforma, granulomatous nodules, leukoderma and pigmented contact dermatitis are increasingly recognised. A further complication in patient diagnosis and management is the need to evaluate the role of ultra violet light or underlying skin diseases in the presentation.

Any chemical can be implicated in this condition provided exposure occurs. Most exposures are identifiable by the distribution of the skin condition on the body, which usually corresponds to sites of contact. This may be immediately obvious such as eczema of the earlobes due to metals like nickel or gold, released from earrings. It may be subtle requiring more investigation to establish the cause, for example involvement of the exposed areas of the skin due to some airborne exposure and/or photosensitivity. A generalised symmetrical dermatitis can occur in association with localised contact dermatitis as a consequence of a hypersensitive skin state induced by the ongoing chronic antigen stimulation. This is known as an id reaction and is often not recognised as a complication of contact eczema.

Contact dermatitis can be found in any setting. Although previously thought to be rare in children it is now increasingly being described. In the occupational setting it is especially important and accounts for a significant proportion of work related disease. With increasing exposure to chemicals in all aspects of daily living, the incidence of contact dermatitis will increase. The public should be aware that because a product is пїЅnaturalпїЅ, produced by a cosmetic house or sold in a supermarket it does not mean that it will not cause contact dermatitis. Likewise it is not only the introduction of a new product that should alert one to the source of exposure. Contact dermatitis may develop after having used a product for some time for many reasons. Manufacturing conditions may have altered, raw material sources changed or formulations been modified introducing a new chemical or changing the concentration of one already present thus increasing the risk of causing a skin problem with ongoing exposure. Cumulative damage to the skin caused by irritants like excess water, detergents or low humidity predisposes to allergy.

The skin forms a living, selective, barrier interface between the environment and the body. The main barrier for most substances is located in the stratum corneum, is a few microns thick and comprises the intercellular lipid lamella membrane domain between corneocytes. This barrier has developed to function at an air-liquid interface and is easily destroyed by exposure to chemicals, especially solvents and detergents, dehydration and excess moisture. These repeated insults act in an additive and sometimes synergistic way, causing dysfunction of the barrier. A damaged barrier becomes clinically evident when the disease threshold for that person is reached. The first manifestation is a dry skin, which gradually deteriorates into eczema if the initial warning signs are ignored. Chronic irritant exposure stimulates a reactive state in the epidermis causing acanthosis and hyperkeratosis, know as skin hardening, the skinпїЅs attempt to protect this vital barrier. This non-immune response constitutes irritant contact dermatitis. Every individual can develop irritant contact dermatitis if exposed to environments that cause destruction of the barrier function. This is related to the frequency and duration of exposure plus the intensity of the insult. Individual variation represents individual skin barrier threshold for disease. While clinical signs and symptoms indicate a pathological state it must be remembered that varying degrees of silent, unrecognised, sub-clinical barrier dysfunction have preceded its presentation. Irritant contact dermatitis is preventable and reversible.

The development of irritant contact dermatitis can be assured if the skin is exposed to strong enough irritants, often enough and for long enough.

A dysfunctional barrier means that there is a greater chance that the skin-associated immune system of the affected individual will be exposed to immunogens initiating the immune cascade for the development of type I, urticarial or type IV, cell-mediated hypersensitivity responses. These immune responses constitute allergic contact dermatitis. Only susceptible individuals will develop allergic contact dermatitis. The substances implicated in these allergic reactions are often present in products at low concentrations and are often not suspected. Examples include contaminants of raw materials, substances formed in the manufacturing process, breakdown products or alterations in formulations. They may be used widely as they are perceived as low risk substances generally but for the individual that develops an allergic reaction they can have devastating effects on the skin. Examples include preservatives, anti-oxidants, perfumes, penetration enhancers and anti-bacterial agents amongst others.
The concentration of the immunogen required to initiate the immune response is usually higher than that required to trigger it.
Recommended exposure levels for the prevention of allergy are thus possible. The 1994 EEC Nickel Directive limits nickel exposure from items in prolonged contact with the skin, such as jewellery. A decline in the incidence of nickel sensitive individuals in countries that have adopted and implemented these recommendations has been reported. In sensitised individuals however the same exposure levels may be meaningless as the immune response is triggered at much lower concentrations of the allergen. Skin disease is thus precipitated and maintained with ongoing low level exposure


What is not looked for is not found!

The single most valuable investigation in type IV contact dermatitis evaluation is patch testing. While the test is easy to perform and read when standardised allergen preparations are used the relevance and interpretation of the results requires experience and expertise. Most routine testing offered in South Africa employs a standard series of the 20 most common allergens encountered in Europe. The relevance of this choice of allergens to Southern Africa has not been established. The choice of substances for inclusion in a standard series varies regionally, the North America and Japanese have their own respective standard series. The limited number of chemicals tested in a standard series relative to the large number of potential allergens encountered daily, highlights the limitations of the test findings. Because all chemicals are irritants it is especially important that testing with the patientпїЅs own products is performed at a centre of expertise. This ensures that the product is correctly diluted in the appropriate vehicle for the results to be interpretable. Negative results thus do not exclude allergic contact dermatitis and neither do positive results confirm an allergic component.


All patch test results must be evaluated for relevance.

Irritant contact dermatitis is a clinical diagnosis and patch testing is not required. As it results from barrier dysfunction it predisposes to allergic contact dermatitis and thus the two frequently occur together. Should adequate avoidance of irritants not result in the gradual improvement of suspected irritant dermatitis then an allergic component should be excluded.

Patient management, once relevance has been established, requires that the care-giver have sufficient knowledge of the sources of the allergen and cross reacting compounds to be able to provide practical advice for all activities of daily living. Because there are no product ingredient labelling directives in South Africa this is very difficult. In the USA and EEC ingredient labelling legislation ensures patients can avoid products containing the principal or cross-reacting allergens.


Allergy testing requires expertise to ensure relevance and appropriate patient management.

How to cope with contact dermatitis

Keep life simple!

Control the disease
The aim is to settle inflammation and make the patient comfortable. Usually potent topical steroids are used for a short time and these are then gradually weaned until no longer required. While investigating the cause of the problem, treatment may be needed intermittently to control flares.

Remember that contact dermatitis will persist and possibly worsen if exposure continues despite topical treatment.

Protect the skin

Prevent skin barrier damage by limiting exposure to irritants like excess moisture, dry conditions, solvents, soaps and detergents. Use a bland cream (aqueous cream) as a soap substitute and regular emollient.

Limit exposure

Seek professional help to identify the cause of the skin problem. Once this has been found, research were the substance can be found and avoid exposing the skin to these sources. Identify safe alternatives. Ask about cross reactions with other related products.

Avoiding contact prevents contact dermatitis

Patient education

This is central to controlling contact dermatitis and repetition may be necessary before adequate understanding and co-operation is achieved.

The South African Initiative

In order to establish a standard series of allergens relevant to Southern Africa and monitor changing trends, a national database of patch test results needs to be set up. Simultaneously, information on product ingredients needs to be gathered and added to the database to allow for the generation of patient information lists advising on products to avoid and alternates that are safe to use with specific allergies. This data and information should be co-ordinated through a centre of expertise and readily available to healthcare providers and patients.

The University of Cape Town Skin and Hair Centre houses an established referral centre for contact dermatitis and occupational skin diseases. Initial contact with relevant healthcare providers has indicated that national co-operation regarding data collection can be expected. As a national resource centre, a supply of commercial and local allergens will be built up and made available to interested healthcare providers as needed. Alternately, patients can be referred for patch testing, either at the centre or at the work place. The centre will offer courses in contact dermatitis and occupational skin disease and advise on specific problems. Patients can be reviewed on a referral basis.

For further information contact Professor Gail Todd of The Department of Dermatology at:


Telephone (021) 404-3376 or (021) 406-5890
Fax (021) 447-8232
Email [email protected]

Copyright: Allergy Society of South Africa 1993

This information sheet is freely available from:

ALLSA
P.O. Box 88
Observatory, 7935
Cape Town, R.S.A.

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