Common dermatoses

Non-atopic dermatitisnatalie stone

Abstractthe term ‘dermatitis’ is synonymous with the term ‘eczema’. Whilst

atopic dermatitis is the commonest form of eczema seen in childhood,

a variety of clinical patterns, particularly in adults are recognized. Hand

eczema and contact dermatitis may occur outside the setting of atopy, as

may varicose, discoid, seborrhoeic, and asteatotic dermatitis. this article

focuses predominantly on contact eczema.

Keywords allergic contact dermatitis; irritant contact dermatitis; patch

testing; type IV hypersensitivity reaction

Hand eczema

The incidence of hand eczema in the general population is esti-mated to be 2%. Its greatest impact is as an occupational derma-tosis, particularly in professions where there is much wet work, such as nursing, catering, hairdressing.

As with all other types of eczema, this is a non-specific term with multifactorial causes for the eczema often being present. The main differential diagnoses are psoriasis and fungal infec-tion. Atopic eczema is a common cause of endogenous hand eczema, particularly in adults. Exogenous causes include irritant and allergic contact dermatitis.

Management1: avoidance of irritants, regular use of emollients and moderately potent/potent topical steroids. Patch testing should be performed in all cases of chronic hand eczema to exclude associated allergy. Salicylic acid preparations can help with hyperkeratotic changes. Secondary infection should be treated either with topical or oral antibiotics and/or with topi-cal antiseptic solutions such as dilute potassium permanganate for acute weeping skin. Tacrolimus can be considered if topical steroids have failed and/or caused side effects. PUVA light treat-ment can be of benefit to patients with refractory hand eczema. Where topical treatments have failed, oral immunosuppression with azathioprine may be tried. Alitretinoin is a new retinoic acid derivative licensed specifically for severe chronic hand eczema unresponsive to potent topical steroids.

Varicose eczema

Varicose eczema is a common condition affecting the skin of the lower legs, secondary to venous hypertension. It is usually

Natalie Stone FRCP is Consultant Dermatologist at the Royal Gwent

Hospital, Newport, UK. Competing interests: none declared.

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therefore associated with varicose veins or a history of deep venous thrombosis. Patients present with a red, scaly, itchy rash on the lower legs, which can sometimes go on to form a more widespread eruption.

This is a constitutional form of eczema, but it can be exacer-bated by irritant dermatitis because of washing with soaps etc, and/or by allergic contact dermatitis. Allergy is a common cofac-tor in this group because of use of topical antibiotics, lanolin in emollients and rubber in bandages.

Management: avoidance of irritants, regular emollients to wash and moisturize and moderately potent topical steroid ointments. Ointments should be used instead of creams if possible, due to their lower risk of inducing allergy. Doppler examination should be performed and compression hosiery used if no arterial insuf-ficiency found. Patch testing should be performed if concomitant allergic contact dermatitis is suspected.

Contact dermatitis2

Contact dermatitis refers to an eczematous rash caused by con-tact with an external substance. It is classified as exogenous eczema (caused by external factors), as opposed to endogenous eczema such as atopic eczema.

Contact dermatitis is divided into two distinct types: • irritant contact dermatitis • allergic contact dermatitis.

Irritant contact dermatitis results from direct damage to the skin by chemicals and/or physical irritants (e.g. hand eczema from excess exposure to soaps and detergents). Allergic contact dermatitis is an immune-mediated, type IV hypersensitivity reac-tion to a specific allergen (e.g. scalp/facial eczema from para-phenylene diamine in hair dye, foot eczema from chromate in leather shoes).

The dermatologist’s role is to diagnose the underlying cause of eczema, be that endogenous (e.g. atopic) or exogenous due to irritancy or allergy. Frequently the types of eczema overlap, such that more than one type of eczema occurs in the same patient. Patients with atopic eczema have a predisposition to develop-ing irritant contact dermatitis. Irritant dermatitis can predispose to the development of allergic contact dermatitis because of the

• new allergens are continuing to be discovered, such as

hydroxydecyl ubiquinone in anti-ageing creams

• Well-known allergens are causing problems in new situations,

such as paraphenylene diamine (in permanent hair dye) being

added to temporary black henna tattoos and acrylates in

artificial acrylic nails

• some common allergens are reducing in prevalence with

new european legislation, such as the ban on the use of

preservative methyldibromoglutaronitrile in personal care

products

What’s new?

6 © 2009 Published by elsevier Ltd.

Common dermatoses

inflammatory cytokines present, and reduced barrier function of the skin to allergens.

Irritant contact dermatitisIrritant contact dermatitis is inflammation of the skin caused by exposure to an external agent causing non-immunological dam-age to the skin barrier function. It may be acute (e.g. accidental spillage of acid onto the skin) or chronic (e.g. repeated exposure to washing-up liquid, wet work). It is the most common form of contact dermatitis and is particularly common in professions involving wet work and chemicals (e.g. cleaning, hairdressing, metalworking and food preparation).

Pathogenesis: irritants are physical or chemical agents that cause cutaneous damage when in contact with the skin. Irritancy var-ies depending on the potency and concentration of the irritant, the frequency and length of time it is in contact with the skin, occlusion of the irritant on the skin (e.g. inside a rubber glove) and individual predisposition to irritancy (e.g. atopic eczema). Common physical and chemical irritants are listed in Table 1. Memory T lymphocytes have no role in the initiation of this reac-tion. The histological appearances of irritant and allergic contact dermatitis are similar.

Potent irritants are chemicals such as strong alkalis and acids. Individuals with atopic eczema or active eczema of another cause are at greater risk of developing an irritant dermatitis due to the cumulative effect of weaker irritants such as soap and water. The hands are a common site.

Clinical features: the severity of acute irritant dermatitis ranges from transient redness of the skin, mild dryness and dermatitis, to florid skin necrosis, blister formation and ulceration (chemical burns). Chronic irritant dermatitis usually affects thinner skin at frequently exposed sites. The classical pattern of irritant hand eczema involves the finger webs, where water and soap accumu-late, and the backs of the hands, where the skin is thinner and therefore more susceptible.

Management and prevention: management of irritant contact der-matitis comprises mainly prevention and protection of the skin from irritants. Health education for workers is also of importance.

Acute irritant dermatitis - risk management in the workplace should be used to minimize accidental chemical spills. Appropriate

Common irritants

Physical Heat

Humidity

Friction

Chemical detergents/wet work

acids (e.g. hydrochloric, sulphuric, hydrofluoric)

alkalis (e.g. potassium hydroxide, wet concrete,

gold cyanide)

organic solvents (e.g. acrylonitrile)

organic and inorganic salts (e.g. arsenic)

Table 1

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gloves, goggles and other personal protective equipment (PPE) should be used when handling known irritants. It is important that the correct type of glove is used for the particular chemical being used.

Chronic irritant dermatitis - children with predisposing skin problems such as atopic eczema should be encouraged to avoid careers in high-risk occupations such as hairdressing. Use of appropriate PPE and minimization of contact with irritants is important. The barrier creams used at work are often irritant and are thought to have no real role in prevention, but use of emol-lient after work is thought to be helpful. Exposure to irritants at home should also be minimized. Use of soap and detergents should be discouraged and emollients substituted. Topical corti-costeroids are often helpful.

Allergic contact dermatitisAllergic contact dermatitis (ACD) is an eczematous reaction in the skin caused by exposure to an allergen to which the indi-vidual has been previously sensitized.

Pathogenesis: allergic contact dermatitis is a type IV delayed hypersensitivity reaction. There are two phases in the develop-ment of allergic contact dermatitis: initial sensitization and then elicitation of the reaction. • Sensitization occurs when an allergen penetrates the skin and binds to Langerhans’ antigen-presenting cells. The Langerhans’ cells then migrate to the lymph nodes, where they sensitize na-ive T-cells. The sensitized T-cells then travel back to the skin throughout the body. • Elicitation occurs when the same allergen is again in contact with the skin, is presented by the Langerhans’ cells and is recog-nized by sensitized T lymphocytes. An inflammatory reaction is triggered, with an influx of further white blood cells and release of cytokines.

Clinical features: allergic contact dermatitis usually presents with an eczematous rash at the site of contact with an allergen (Table 2), although ‘systematization’ (spreading of the rash to other sites) can also occur. Common sites are the hands, face, anogenital area and lower leg (particularly in association with leg ulcers). Patients who have repeatedly used multiple topical medicaments, particularly to sites that are occluded (such as under a bandage), are at particular risk of developing ACD.

Nickel allergy is common, affecting 10% of women and 1% of men in Western countries. It is mainly caused by the pres-ence of nickel in jewellery, watch straps and clothing studs. New

Common allergens

• nickel (metal)

• Fragrance

• rubber (antioxidants/accelerators added to rubber)

• Chromate (metal in leather and cement)

• Formaldehyde (preservative in cosmetics/shampoos)

• Colophony (glues, pine trees, adhesive plaster)

Table 2

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Common dermatoses

legislation has ensured that the nickel content of items in close contact with the skin is low and the prevalence of the allergy seems to be declining.

Allergy to fragrances in soap can lead to hand eczema; air-borne dermatitis affecting the face and neck can be caused by air fresheners and perfumes.

Investigations: patients with eczema that is resistant to treat-ment or has an unusual distribution should be referred for patch-

figure 1 multiple allergens are applied to the back in separate

chambers and removed after two days.

medICIne 37:5 24

testing to investigate possible type IV allergy. Specific allergens are applied to the back under occlusion (Figure 1), then removed 2 days later and a first reading taken. A second reading is taken after 4 days. Positive readings are interpreted as allergic or irri-tant depending on their morphology, and are then interpreted with respect to their relevance to the patient.

Management: patients with allergic contact dermatitis should be counselled and given written advice about what they are allergic to, where they are likely to encounter the allergen and how best to avoid contact with it. General skin-care advice should be given regarding avoidance of irritants, use of moisturizers and use of appropriate topical corticosteroids when needed. Despite strict avoidance of allergens, however, some patients may require sec-ond-line treatment such as light therapy or oral immunosuppres-sants to control their dermatitis. ◆

RefeReNCes

1 Van Coerorden am, Coenraads PJ, svensson a, et al. overview of

studies of treatments for hand eczema. Br J Dermatol 2004; 151:

446–51.

2 rycroft rJG, Frosch PJ. textbook of contact dermatitis. Berlin:

springer-Verlag, 2001.

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