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Contact dermatitis and other occupational skin diseases

Contact dermatitis and other occupational skin diseases

Contact dermatitis

Contact dermatitis is by far the most common form of occupational skin disease and is an important source of time lost from work and a long-term disability. Contact dermatitis is caused by external agents, which may be present at home, at work or at play. Contact dermatitis has an irritant rather than an allergic cause in at least 70% of patients. It is not easy to separate the irritant from the allergic causes by the clinical or histological appearance of the lesions. Irritants may cause damage by either once only exposure to the high concentration of an irritating chemical or, more commonly, repeated exposures to low concentrations of minor irritants.

Management of all forms of contact dermatitis is complicated by the need for different treatments at different body sites, the presence of more than one contributing contactant, the fact that home and play environments may be further adding to work-related problems, and the potential for all topical therapies to aggravate an existing dermatitis. In all instances the principle is to remove the offending contactant, treat the residual disease and prevent recurrence. It should also be stressed that healing after contact dermatitis is often slow, not always assessable by visible means and frequently retarded by the return to full pre-injury work activity because the skin looks or feels normal.

General problems in the management of contact dermatitis

Ensure that other possible causes, particularly infective or endogenous causes, such as psoriasis, have been excluded. These likely other causes are set out in Table 1.

The visible healing time and the length of time afterwards during which skin damaged by contact dermatitis remains abnormal is always underestimated by the patient, medical attendants and work supervisors.

It is important to emphasise this to the patient, as the patient will often suspend therapy once symptoms stop even though skin is visibly abnormal. Protective practices must be followed even after the skin returns to normal. Failure to observe these simple principles is a major reason for the poor prognosis, particularly in hand dermatitis.

Only very small amounts of the chemical are required to cause severe allergic contact dermatitis, which often spreads away from the initial site. Irritant dermatitis can sometimes be avoided by the modification of work practices or the use of protective clothing. Obviously factors such as lack of alternative employment and a particular liking for the job may encourage a person suffering from contact dermatitis to stay in the same job.

A site visit is most likely to be worthwhile when a job change is being contemplated or there is insufficient protection from irritants as aggravators, eg hand cleaners and washing practices. Sometimes an unsuspected allergen or irritant may be detected by a site visit.

It is important to establish the daily routine of the patient with particular reference to showering, cleansing and clothing. The presence of particulate matter in the work atmosphere and the temperature of the work environment under variable conditions should also be noted. Recommendations may then be made for appropriate adjustment to work practice or physical protection.

Relapse is most commonly caused by failure to maintain preventative measures. However, if there is sudden worsening, think of possible development of an additional allergic contact dermatitis. Common causes include preservatives in creams, or gloves used to protect damaged skin. Worsening may also be associated with infections, usually staphylococcal, corticosteroid allergy, or environmental change at home or at work.

Patch testing is a form of investigation usually carried out by dermatologists to identify or confirm the allergens involved in allergic contact dermatitis. The standard technique involves the application of a series of disks containing potential allergenic chemicals strapped with tape to an area of skin, usually on the back, and left in place for 48 hours. It is usually read at 48 hours when the patches are removed and again at 72 or 96 hours to see if there are any late reactions.

Positive reactions do not always distinguish initially between irritant and allergic reactions, although internationally standardised concentrations of the chemicals applied are selected to avoid the problem of irritant potential. Persistence of a positive reaction at 48 hours after removal usually indicates allergy. Reported results of patch tests should be interpreted with care.

False positive results may be irritant reactions or reactions due to heightened sensitivity of the area of skin tested to a number of allergens with potential irritant capacity. Positive reactions may be irrelevant to the current clinical problem.

False negative reactions may be seen when there is immunosuppression, either general or in the area of skin tested, or when the presentation of allergen does not replicate the physical and environmental conditions which allow absorption of the allergen at the site of the dermatitis. This latter situation is often present with components of shoes that are tested for shoe dermatitis.

Patch testing is most useful in the following situations.

           When a clinically unsuspected allergen that may be relevant is discovered.

           When worsening of an irritant contact dermatitis cannot be explained by environmental circumstances, and the possibility of superimposed allergic contact sensitivity should be strongly considered, eg rubber glove dermatitis, vehicle preservative dermatitis.

           Plant or shrub dermatitis when the clinical condition suggests this possibility. Patch testing can be performed using the leaf of the suspected plants strapped to the inner forearm for 24 hours.

           The suspected presence of multiple sensitivities in patients with allergic contact dermatitis not responding to avoidance of the anticipated allergen.

           When contact dermatitis appears to complicate other existing forms of dermatitis, such as atopic dermatitis and seborrhoeic dermatitis.

           The identification of the allergenic component in a multicomponent substance such as a cream, where the allergen may be the active ingredient or the preservative. If the preservative is responsible then creams containing this preservative, will need to be avoided.

Sometimes when substances, creams or clothing need to be trialled as alternatives then a usage test may be helpful. Every effort should be made to reproduce the environmental conditions likely to be operative when the substance is used. For creams, repeated open application to the cubital fossae may be used.

Regional management of contact dermatitis

The major features, including differential diagnosis, likely allergens or irritants involved, potency of topical corticosteroid and adjunctive therapies for various regions, are set out in Table.1. Further detail for specific areas is set out below.

Avoidance of causative factors - The usual allergens or irritants are set out in Table 1. Avoid irritants such as soap, detergents, water, oils, grease and generally dirty jobs that require strong cleansers to remove the dirt and grease. Although there is no true barrier cream which will in any way restore the altered barrier of hands suffering from dermatitis, the use of emollients such as emulsifying ointment may be helpful where it is practical to apply them.

Cloth or leather gloves are preferable where it is not necessary to avoid wet contactants, eg protection from dust, friction, grease, soil and some oils. Where protection from liquids is required then PVC or rubber gloves become necessary. See below for the specific problems relating to the use of rubber gloves.

Topical therapy - The general principles of treatment of dermatitis apply here.

In the acute phase, soaks or wet dressings, see Specific treatment of dermatitis, will usually help to dry up the acute and weeping lesions. Use

aluminium acetate soaks OR potassium permanganate soaks OR saline soaks OR wet dressing with tap water, for 10 to 15 minutes, 1 to 3 times daily depending on the degree of exudation.

Secondary infection frequently complicates acute contact dermatitis of the hands. If this is suspected or confirmed by bacterial swab, appropriate systemic therapy should be instituted, see General treatment of dermatitis: antibiotic therapy.

In the acute phase, the use of topical corticosteroids, where practical, may help contain the inflammatory process. Use

a moderately potent topical corticosteroid, applied 3 times daily.

In general, creams are better than ointments for this phase.

On the palmar surface of the hands, stronger corticosteroids are indicated for the acute phase, for example

a potent to very potent topical corticosteroid, applied 3 times daily.

In severe acute cases, oral corticosteroids may be required. Use

prednisolone 25 to 50mg orally, daily for 1 to 2 weeks then reduce the dose gradually over 1 to 2 weeks.

In the chronic phase, as erythema subsides and the vesiculation settles, the dominant problem on the palmar surface of the hands is one of dryness and painful cracking on movement. At this stage frequent use of moisturisers is indicated. Use

glycerol 10% in sorbolene cream OR propylene glycol 40% in aqueous cream OR white soft paraffin OR a proprietary emollient hand cream.

The main requirement is frequent and adequate lubrication during the day.

Unless there is significant erythema or recurring vesiculation, potent topical corticosteroids have limited use in the chronic stage. If it is cosmetically and functionally acceptable to use greasier ointment bases then this is preferable at the stage of dryness and cracking. Corticosteroids should be avoided when there is obvious thinning of the skin on the dorsal or palmar surface of the hands, or repeated fissuring. Occlusion, see Modified dressings, helps deep fissuring but may be difficult to use on hands.

Rubber glove dermatitis - This is becoming an increasingly serious problem with the emergence of life-threatening anaphylaxis for a small number of people who have developed immediate reactions to the latex rubber proteins in gloves.

Delayed contact dermatitis - The most common form of dermatitis related to rubber gloves is a delayed hypersensitivity contact dermatitis associated with allergy to rubber components other than latex protein, eg accelerants and oxidisers used in the manufacturing process. Irritant contact dermatitis from frictional factors is also a frequent problem with wearers of rubber gloves.

Urticaria from contact with rubber latex occurs within 15 to 30 minutes of wearing of the glove. It is IgE mediated. It may extend well beyond the area of glove contact. Those particularly at risk include medical workers, dentists, and lay people who frequently have to use rubber gloves, eg spina bifida patients and their carers. Diagnosis is by radio-allergosorbent test (RAST),  although if negative, prick testing utilising a solubilised form of the glove may be necessary. Prick testing should always be done in a controlled situation such as an allergy department.

To assist in prevention:

           use high quality rubber gloves

           use unpowdered gloves, as this reduces the incidence of protein contact dermatitis from the gloves

           avoid latex rubber gloves when the hands are already damaged with dermatitis.

If severe latex rubber protein allergy has developed:

           use alternative (nonlatex) gloves for wet work

           avoid any fruits and vegetables that cross-react with the offending allergen, eg banana and avocado

           patients may need to carry their own adrenaline in case of a severe anaphylactic reaction

           warn patients of the risk of exposure to related products during some medical procedures (eg where doctors or dentist are wearing rubber gloves; latex lined instruments for intubation), although this is increasingly being avoided because of awareness of risk amongst medical personnel.

Cosmetics are a relatively uncommon cause of allergic contact dermatitis on the face, but may frequently cause irritation in atopic patients or patients with sensitive skin, particularly those with a tendency to rosacea. All cosmetics should be ceased, then tested in the cubital fossae before being used on the face again.

Avoid airborne irritants or allergens if concomitant involvement of the neck and arms suggests their involvement.

Remember that allergens may be transferred from fingers (eg nail polish) or hands (eg wiping the face while wearing gloves).

To reduce inflammation, use

a moderately potent to potent topical corticosteroid for no longer than 1 week for discussion of the use of topical corticosteroids on the face).

Most contact dermatitis of the face should settle within 1 week with adequate treatment. If not, consider other diagnoses.

Ointments used on the face can induce acne and are often cosmetically unacceptable, but have the advantage of not containing preservatives where the possibility of an allergic reaction to one of the preservatives is suspected. Although uncommon, allergic contact dermatitis to the corticosteroid itself, particularly hydrocortisone, can occur and complicate recovery.

Contact dermatitis can complicate most of the conditions listed in Table . as differential diagnoses and several of these conditions may also complicate contact dermatitis, eg psoriasis, tinea or candidiasis.

Avoid possible allergens or irritants, eg soaps, cleansers and hygiene sprays, particularly in the perianal, vulval and penile area. Reduce friction caused by clothing and sweating.

Treat secondary bacterial, fungal or yeast infection.

To reduce inflammation, use

a moderately potent topical corticosteroid.

Potent corticosteroids should not be used on the scrotum because of the high absorption from this area, and should not be used in the perianal region or skin folds because of the risk of skin thinning.

Sometimes, particularly with acute vulval, penile or scrotal rashes, the degree of inflammatory reaction and swelling is great enough to warrant a short course of oral corticosteroids. Use

prednisolone 25mg orally, daily for a maximum of 1 or 2 weeks then reduce the dose gradually over 1 to 2 weeks.

Contact dermatitis of the feet frequently occurs because of the excessive sweating which encourages friction and tends to leach allergens out of footwear or socks. Therefore reduce sweating, using

diphemanil methylsulfate 2% dusting powder OR aluminium chloride hexahydrate 20% solution.

The wearing of heavy work boots in hot surroundings should be avoided. Other measures such as avoidance or changing of shoes, or at least the wearing of thick socks to act as a barrier, may be necessary.

Where dryness and cracking is a major feature, emollients are helpful.

glycerol 10 to 20% in sorbolene cream OR urea 10% (with or without lactic acid 5%) cream.

To reduce inflammation, use

a potent topical corticosteroid.

For severe or refractory cases, a short course of oral corticosteroids may be required. Use

prednisolone 25mg daily for a maximum of 1 to 2 weeks then reduce the dose gradually over 1 to 2 weeks.

If there is still no response, consider referral to a dermatologist where other treatment options include phototherapy.

Contact dermatitis: Summary of points by region (Table 4.15)

Other occupational skin diseases

Acne-like lesions and folliculitis occur in areas of heavy oil exposure such as the thighs and forearms. Comedones, furuncles and carbuncles can occur.

Treatment consists of

           avoidance of prolonged contact with oils and greases

           frequent changes of oil-soaked clothing

           daily showering

           avoidance of excessively hot environments, which may precipitate a flare of truncal lesions.

Additional treatment, including systemic antibiotics and rarely isotretinoin, may be necessary.

Chloracne is characterised by excessive comedo formation and distinguished from acne by the history of exposure to chloracneigens including chlornaphthalenes and polychlorbiphenyls found in pesticides. Chloracne is further distinguished by the relative absence of inflammatory lesions or seborrhoea and a distribution including the axillae, scrotum and malar crescent of the face. Treatment is much less effective, although withdrawal of the offending agent is the prime consideration. Antibiotics and isotretinoin,  have proved to be less effective than in other forms of acne. Causal agents of chloracne may also cause systemic abnormalities, eg abnormal liver function.

By far the most common source of problems is exposure to ultraviolet radiation (UVR) in the course of employment. Sources of UVR include natural sunlight as well as arc welding and germicidal ultraviolet.

The contribution of other environmental carcinogens such as polycyclic aromatic hydrocarbons is most likely to be additive rather than causative in modern industry.

Prevention should include a protective work environment and clothing where possible, as well as a thorough evaluation of the past history of sun exposure, skin type, present solar damage and family history of skin cancer for all potential outside workers.

For treatment of established skin cancer.

Paronychia is a common problem amongst those exposed to repeated wet work, eg food handlers and bar attendants.

Treat paronychia by:

           avoidance of wet conditions where possible

           protection from further damage by physical means, eg use of gloves

           frequent use of emollients.

Acute bacterial infection or chronic yeast infection should be treated appropriately when present.

Abnormal nail plates, as evidenced by discolouration, leukonychia or koilonychia (spoon-shaped nails) could all be induced by repeated exposure to friction, pressure or chemical irritants. The only effective treatment of this condition is avoidance of the cause, and increased protection of the nail plate using.

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