Auckland Allergy & Eczema Clinic

Contact Dermatitis

Occupational (Contact) Dermatitis

  • What is it?
  • How is it caused in the occupational environment?
  • How should it be managed?

In current terminology "dermatitis" is used synonymously with "eczema" to describe inflammatory reactions in the skin, which are typically characterized by itching and redness but may vary from slight thickening of the outermost layer of the skin with small fissures to extensive redness, swelling and oozing.

Dermatitis may be entirely endogenous (constitutional) or be entirely exogenous (contact). Exogenous dermatitis or contact dermatitis may be caused by irritant or allergic contact reactions or both. Dermatitis often has a multifactorial aetiology and may be aggravated by the presence of bacterial pathogens such as staph. Aureus. When considering hand eczema it is always worth investigating the possible role of contributory factors and assessing the role of these. Atopic (constitutional) hand eczema is a common example of an endogenous eczema in which exogenous factors normally compound the situation. The other two forms of contact dermatitis are photocontact dermatitis and contact urticaria.

An occupational dermatitis is one where the inflammatory reaction is caused entirely by occupational contact factors or where such agents are partly responsible by contributing to the reaction on compromised skin. In most cases occupationally related dermatitis affects the hands alone, though they may spread onto the forearms. Occasionally, the face may be the prime site on inflammation, as in the case of airborne contact factors.

Contact dermatitis accounts for at least 60% of occupational skin disease, which, in turn, account for 40-70 % of occupationally acquired illness.

Irritant Contact Dermatitis

Approximately 75% of contact dermatitis is due to irritants.

Irritant contact dermatitis with synonym toxic, traumiterative, or housewives eczema and non-allergic contact dermatitis is the most common variant with a point prevalence of 1-2% in the healthy population. Localized almost exclusively to the hands it occurs most frequently in ‘wet work’ occupations such as hairdressers, healthcare personnel, cleaners, cooks and caterers. Contactants are detergents and surfactants, acid and alkali solutions, organic solvents, sometimes even water. The deleterious effect of these agents is the removal of the fat emulsion on the skin surface, a damage to the function of the epidermal skin barrier, and removal of the water-binding substances of the outer layer. The single exposure is usually harmless but by accumulation destructive. The clinical consequences are dryness, scaling and fissuring, progressing to eczematous dermatitis. It occurs where the skin is thinnest. Hence, it is often seen in the finger webs and back of the hands rather than the palms. The most common predisposing factor for this type of contact dermatitis is the presence of an atopic predisposition.

Allergic Contact Dermatitis

Allergic contact dermatitis is the clinical expression of contact allergy. This type of hypersensitivity is always acquired and may develop any time during life. The allergy-inducting agents or antigens are low-molecular so-called haptens.

The dermatitis develops at the site of skin contact with the allergen. Secondary spread may occur. Contaminated hands may spread the allergen to previously unexposed sites. Trivial or occult contact with an allergen may result in persistence of dermatitis. Some allergens are essentially ubiquitous — for example formaldehyde and nickel.

It is not yet possible to determine an individual’s susceptibility to developing contact allergy. Hypersensitivity is specific to a particular molecule or to molecules bearing allergenic sites. Although hypersensitivity may eventually be lost, the state should be considered to last indefinitely.

Common occupational allergens

  • Rubber accelerating chemicals, such as thiurams and carbamates
  • Biocides — such as formaldehyde
  • Hairdressing chemicals — such as thioglycolates, phenylediamine
  • Epoxy resin monomers
  • Chromates
  • Plant allergens — such as sesquiterpene lactones found in Chrysanthemum.

Contact Urticaria

Contact urticaria deviates from regular contact dermatitis in the type of clinical reaction, its time sequence, the causal agents, and the pathogenic mechanism. True, the clinical reaction appears on the site of direct contact, usually the fingers, but consists of small itching wheals, emerging within 10-20 minutes after contact and rapidly disappearing. Causal agents may be latex rubber in gloves, animal proteins or other foodstuffs, the patients often being health care personnel, as well as chefs and workers in meat and fish industry.

Pertinent allergens are high-molecular, complete antigens, normally not absorbed through the skin. Therefore, a precedent damage to the skin barrier e.g. discrete irritant dermatitis, would be a prerequisite. These patients usually have an atopic constitution.

A regular 48hour patch test will give a false negative reaction. Instead, a short term (20min) prick test with the suspected material e.g. rubber or shrimps as is, will provide a positive, immediate, wheal reaction. In latex cases, also specific IgE antibodies may be demonstrated in the blood (RAST test)

Rubber latex protein sensitivity

Of concern is the increasing occurrence of immediate type 1 hypersensitivity to proteins present in latex gloves. The problem is seen principally in health care workers especially atopics working in the operating theatre or ICU. Prevalence is about 5-10% in US and European hospitals. 12.5% of anaesthesists were sensitized in one US study. Other workers at risk are hairdressers, 10% in one study and glove factory workers 11% in another study.

The significance of this sensitization is that all these patients are at risk for anaphylaxis.

Latex is the second most common cause of intraoperative anaphylaxis.

Photocontact Dermatitis

Photocontact dermatitis is the result of an interaction between a harmful substance present in the skin and ultraviolet radiation. In other words, no dermatitis evolves by the absorbed photosensitizer alone (e.g. if the subject stays indoors) but UV exposure is also required. Photocontact dermatitis is therefore always localized to light-exposed skin, viz. on face, ears, dorsal aspect of hands, and other areas not protected by clothing. Common phototoxins are found in ubiquitous plants of the Umbelliferae family (parsnip, fennel, carrot & celery), therefore sometimes seen in farmers. Plants from the compositae family like chrysanthemum cause a volatile pattern and may present as a light-aggravated or ‘exposed site’ dermatitis

Management of Occupational Dermatitis


Understanding the patient’s job is necessary. A job title is not sufficient for this understanding; the question to be asked is not "what do you do?" but "What exactly do you do and how do you do it?" The title "engineer " can mean anything from a desk bound professional to a lathe worker exposed to soluble coolants.

A site visit — watching the patient working – may be necessary.

The history of the dermatitis may provide clues as to the aetiology.

Irritant contact dermatitis may occur as an "epidemic" in a workplace if hygiene has failed, while allergic contact dermatitis is usually sporadic.

Evaluation of contact factors — The evaluation of irritant factors is always subjective. Evaluation of allergic contact factors is objective and provided only by diagnostic patch tests. Properly performed, patch tests will show the presence or absence of important allergens. Patch testing is the only method for the objective evaluation of dermatitis. There are major pitfalls in the use of this essential tool — proper training and experience is essential if it is to provide valid results.

A competent assessment requires all of the above followed by recommendation on reducing or stopping exposure to the offending agent and similar ones.


The diagnosis of an occupational dermatitis should describe thoroughly the nature of the condition, including any endogenous or aggravating factors. Delays in diagnosis that result in continued exposure to relevant irritants or allergens can adversely affect the prognosis.

Standardized Patch Test

  • Test substances appropriately diluted. Standardized kits available.
  • Apply the patch to the upper or mid back.
  • Leave the patch in place and keep dry for 2 days before removing.
  • Read tests:
    • The same day that patches are removed
    • One additional reading 3, 4, or 7 days after test initially applied
  • Grade test reactions according to intensity : 0 = no reaction to 3+ = small blisters
  • Relate relevance of positive reactions to clinical dermatitis cautiously. Careful history and review of skin exposures must establish significance.

Additional Tests

Open application of a suspected allergenic product twice daily for a week to an area on skin or Repeat Open Application Test (ROAT)

Prick Test for evaluation of contact urticaria

Chemical analysis of environmental materials to determine whether they contain a substance to which the patient is patch test positive.

Treatment of Occupational Dermatitis

Education on Prevention measures & avoidance

  • Primary prevention is aimed at providing appropriate information and protection.
  • Employer and employee should be aware of the potential risks of exposure
  • Education of need for good occupational hygiene
  • Adequate provision of suitable and effective means of reducing exposure
  • Awareness of limitations of personal protection devices

In a study published in Occupational Medicine in Sep. 1997 entitled " Worker education in the primary prevention of occupational dermatoses", The paper reports the evaluation of a skin care education program conducted on a fine chemical manufacturing site where over 1,000 employees are located. Approximately 60% are involved in chemical manufacture. Over a twelve-month period production staff received training in prevention of occupational dermatoses linked to a site-wide poster initiative. The incidence of new cases of occupational dermatoses fell from 70 cases in 1,277 employees to 27 cases in 1,277 employees, before and after the intervention respectively.

Training materials such as video and poster presentations may be effectively used in chemical manufacturing industry as an adjunct to prevention and control of exposure to substances hazardous to the skin. Such methods may also be used in other industries where there are significant risks of occupational dermatitis.

Topical treatment alone may be indicated in mild cases.

Barrier / moisturizing creams

Moisturizers prevent the development of experimental irritant contact dermatitis, and using appropriate moisturizers may also enhance the rate of healing on damaged skin. Individuals regularly exposed to irritants should be encouraged to apply moisturizers frequently in order to minimize dermatitis.

Topical steroids — ointments better for dry skin & creams better for moist, oozing skin

Non alkaline cleansers instead of soap

Systemic Therapy

Oral antibiotics often required for secondary bacterial infection.

Oral steroids may be required in severe acute cases