White : Diseases of the Skin - Eczema and Related Disorders

Table of Contents
This Chapter	All Chapters

Gary M. White & Neil H. Cox

Diseases of the Skin

6	Eczema and Related Disorders

CONTACT DERMATITIS
There are two types of contact dermatitis: irritant and allergic. Irritant contact dermatitis results from damage to the skin from topically applied liquids or chemicals, etc. in the absence of an allergic mechanism, and it includes both acute damage as well as more chronic disease due to repeated exposure. Hand dermatitis is the most common example, but lip-licking dermatitis and various other conditions, where frequent water or chemical contact occurs, are included (Figs 6.38 and 6.39). By contrast, allergic contact dermatitis is mediated through a type IV hypersensitivity or allergic mechanism (Fig.6.40). Patients are allergic to a speciﬁc allergen, and whenever their skin comes in contact with that allergen (in sufﬁcient concentration), an eczematous rash will occur. From a practical point of view, the two types may not only be impossible to distinguish clinically but may even coexist; for example, a building laborer may have irritant dermatitis from cement and ‘wear and tear’, but may additionally be allergic to chromate in cement and plaster.

Irritant contact dermatitis
Etiology and pathogenesis
The hands are the most important site, both numerically as they are a common site for contact dermatitis, and in terms of impact for the patient because hands are so important for function. Patients with hand eczema usually have some precipitating or contributing factor. They may have a history of AD, or their work may expose them to irritants. Housewives may develop a hand dermatitis from housework. The work-up requires an inquiry about a history of AD; occupational activities; exposure to potential irritants and allergens; and daily activities that involve the hands, for example hand washing, cleaning, cold exposure, and wet work (exposure of the hands to water for at least 2 h per day). Patients


Figure. 6.51 Hydrocortisone allergy. Surprisingly enough, allergic contact dermatitis may occur from topically applied topical steroids.


Figure. 6.52 Allergic contact dermatitis to quaternarium-15.

Table 6.5 ALLERGENS COMMMONLY INVOLVED IN ALLERGIC CONTACT DERMATITIS

Allergen	Comments
Antiseptics and antimicrobials	Include thimerosal (thiomersal, merthiolate), quinolines (clioquinol), and chloxylenol. Thimerosal is notable for inclusion in eyedrops, contact lens solutions, vaccines and toxoids. Quinolines are used as an additive in some topical steroid preparations, and impart a yellow color when exposed to air.
Balsum of Peru	A crude test for perfume allergy; also reacts with various essential oils in foods. Present in ﬁr trees.
Benzocaine and related agents	These are local anesthetics used topically; benzocaine is the prototype but others also cause reactions, so a mixture such as Caine Mix III is often used for patch testing. The patient should study the list of ingredients of any medication meant to anesthetize or ‘soothe’ the skin, mucosa, or gums; for example, medications to soothe sore throats, teething babies’ gums, and preparations for insect stings or hemorrhoids.
Carba mix	A rubber allergen (e.g. polyurethane foam rubber).
Cetoaryl alcohol	Emulsiﬁer in creams and cosmetics; check ingredient lists, including those of medical products.
Cinnamic alcohol or aldehyde	Cinnamon flavor and fragrance; some toothpastes, cassia oil, some colas and chocolates.
Cobalt	Mainly found in the same sources as nickel (see below).
Colophony	Also known as rosin, sap of pine trees. In glues, adhesives—anything sticky; Scotch tape, polish for furniture, floors, cars; printer’s ink, solder, violin bow resin, and occasionally eye cosmetics.
Epoxy resin	Two-part glues that must be mixed just before using. Some dental material; some plastics.
Ethylene diamine	Stabilizer in some creams. Cross-reacts with aminophylline when given intravenously. May cross-react with meclizine, tripelennamine, or hydroxyzine.
Formaldehyde	Some photographic chemicals, embalming fluid, fumigants, industrial disinfectants, automotive fluids, manufacturing of plastics and plywood. Some ﬁnishes of fabric. Note that some other preservatives release formaldehyde, so they may need to be avoided; many are also allergenic in their own right.
Fragrance mix	A mix of the eight commonest perfume bases; picks up about 75–80% of patients with contact allergy to perfumes.
Fusidic acid	Antibiotic; allergy to topical preparations may occur.
Latex	Latex gloves such as those prevalent in medical ofﬁces, latex balloons, latex-containing condoms. Foods that tend to cross-react and may cause clinical allergic reactions include avocado, banana, tomato, chestnut, and kiwifruit.
Mercaptobenzothiazole (MBT) and related agents	Rubber allergens: both MBT and a ‘mercapto mix’ are tested (see rubber, below). Pet and veterinarian products.
Para-tertiary butyl phenol formaldehyde resin	Adhesive used in footwear, chipboard, etc.
Plants	Primin (primula family) and sesquiterpene lactone (many plants) are routinely tested in Europe, as well as Compositae (daisy family) in selected cases. See also Rhus.
Preservatives	Preservatives are widely used in cosmetics, especially water-based (shampoos, liquid soaps, etc.), as well as in industrial settings (cutting fluids, emulsion paints, etc.). Note that some may be in creams (but not usually ointments) applied to the skin, so patients need to check ingredient listings if an allergy is identiﬁed. Relevant agents that are often tested include parabens (hydroxybenzoates), imidazolidinyl urea (Germall 115), diazolidinyl urea (Germall 111), quaternium 15 (Dowicil 200), isothiazolinones (Kathon CG), chlorocresol, bronopol, and methyldibromo glutaronitrile (Euxyl K).
Neomycin (Neosporin)	A topical antimicrobial agent. Common in triple antibiotic ointments.
Nickel	The most common offending metal allergen. Most costume jewelry, necklaces, fasteners on jeans, safety pins, etc. Dimethylglioxime is used to test metals for nickel content. There is debate as to the signiﬁcance of nickel in the diet. Some experts recommend a nickel-free diet in nickel-sensitive patients who continue to experience ‘flare’.
Para-phenylenediamine (PPD)	Black dye: most common in hair dye. Not allergenic once set. Some rubbers cross-react, as might para-aminobenzoic acid (PABA), sulfa drugs, or benzocaine.
Potassium dichromate	Causes cement dermatitis, as chromates are found in the powdered form of cement. Leather may contain chromates. Coatings for rust, yellow and green paints, other green items, match heads.
Rhus	Poison oak and ivy. Their leaves have a distinct three-leaflet design from a common node: ‘leaves of three, let them be’.
Rubber	Rubber gloves, polyurethane foam rubber, elastic in clothing, shoes, hoses, belts, adhesives, and tapes. See mercaptobenzothiazole, thiuram mix, and carba mix. The European battery also tests PPD black rubber mix.
Sunscreens	Many sunscreen chemicals can cause allergy. However, the commonest reason for reaction to sunscreen product is perfume allergy, followed by allergy to preservatives in the base cream.
Topical steroids	Allergy to these may be difﬁcult to spot. The usual screening tests are to pixocortol pivalate (hydrocortisone allergy) and budesonide (several cross-reactions).
Wool alcohols	Patients should inspect the ingredient list of anything put on skin. Also known as wool wax alcohol or wool alcohol. Derived from sheep’s wool. The cause of allergy to lanolin.


Figure. 6.53 Hand dermatitis from a cleanser. The doctor should always consider allergic contact dermatitis in a patient presenting with an eczematous eruption. The hands are a common site for both allergic and irritant contact dermatitis, because they come into contact with so many things. This patient was allergic to an ingredient in the cleanser used at work.


Figure. 6.54 Contact dermatitis in a patient with a leg ulcer. There is a high prevalence of contact sensitivity in patients with stasis dermatitis or leg ulcers. Patch testing is often indicated.

with obsessive-compulsive disorders may wash their hands excessively (Fig. 6.41).

Clinical

Red, scaly areas, often with ﬁssuring, can affect any part of the hands in irritant hand dermatitis (Figs 6.42 and 6.43). Patterns do not necessarily correlate with cause; for example, while involvement of ﬁnger webs is common in those using detergents or whose condition is related to frequent hand washing, it does not preclude the possibility of reaction to an allergen. Secondary staphylococcal infection is common. Deep and painful ﬁssures typically indicate such a superinfection (Fig.6.44). If left untreated,

Figure. 6.55 (a) Patch testing. Patch tests detect type IV reactions to external allergens. Batteries of common allergens pertinent to the clinical situation are applied to the back for 48 h. In this case, there were multiple reactions to medicament agents including several topical steroids. (b) Patch test, positive reaction. In this case, allergen 4 (paraphenylenediamine) reacted. Paraphenylenediamine is a black dye, and it is the only patch that leaves a black color. In addition to the black coloration, multiple vesicles and a surrounding erythema are seen. (c) In extreme sensitivity, bullous test reactions may occur even to standard test agents, in this case to nickel. (Panel a courtesy of Daniel W. Shaw, M.D.)

Figure. 6.56 Colophony reaction in a florist. Florists may develop an eczematous reaction of the ﬁngertips to a variety of plant components (see also Fig. 2.24).

Figure. 6.57. Rash due to contact with a ﬁg tree. This patient, without a shirt, was pruning a ﬁg tree. The lesions are linear and haphazardly arranged. The area on the lower left suggests that a liquid allergen ran down the back.

Figure. 6.58 Plant dermatitis. A streaky pattern suggests an exogenous cause, which in this case was a plant.

Figure 6.59 Contact allergy complicating wounds. (a) Bacitracin allergy. This patient developed redness, inflammation, and dehiscence 10 days after a minor surgical excision. Allergic contact dermatitis to bacitracin was the cause. Always consider an allergy when the patient returns with a ‘wound infection’. (b) Adhesive allergy. Allergy about a wound site may also occur in response to the adhesive of the dressing. Note the square shape.

Figure. 6.60 Colophony reaction. Square blisters have developed in this patient with sensitivity to colophony (see also Figs 2.24 and 6.43). These lesions were due to adhesive dressings.

Figure. 6.61 Adhesive dermatitis. Reaction to the adhesive in an ostomy bag.

multiple pustules may develop. AD has been found to increase the risk of hand dermatitis in women.

Differential diagnosis
The main differential diagnosis is from allergic contact dermatitis. Patch testing may be appropriate, particularly in those without any obvious history of exposure to irritants or if the disorder is resistant to standard therapies.
Tinea manus, psoriasis, and scabies are the main other differentials.

Tinea of the hands is usually unilateral, but either irritant or allergic contact dermatitis may be (e.g. dermatitis may be asymmetric in hairdressers, who hold scissors in the dominant hand but wet, chemical-loaded hair between the ﬁngers of the non-dominant hand).

Treatment
The patient should decrease repeated hand washing, and reduce

Figure. 6.62 Allergic contact dermatitis to clothing. (a) An eczematous eruption about the axilla but sparing the inner vault is typical of an allergic contact dermatitis to clothing. Usually, the offending material is newly purchased and was not washed before being worn, and the condition does not recur after the clothing is washed. (b) Allergic contact dermatitis to thongs. The diagnosis is easy when the distribution of the rash replicates the shape of the offending item. (c) Elastic (waistband) dermatitis. This red, pruritic eruption is unmistakably related to elastic in the patient’s underwear. The eruption did not develop until the patient’s wife bleached his underwear, a classic history. This is also known as the bleached rubber syndrome.

Figure. 6.63 Rhus dermatitis. Men working outdoors may carry the Rhus antigen to their penis while urinating. Tremendous edema may result. (Courtesy of Michael O. Murphy, M.D.)

Figure. 6.64 Allergic contact dermatitis to a body lotion. A diffuse allergic reaction to a topically applied lotion may mimic a drug eruption.

Figure. 6.65 Paraphenylenediamine allergy in a hairdresser. Paraphenylenediamine is most commonly found in black hair dye. Hairdressers are prone to this allergy. The non-dominant hand is more severely affected in this patient, because it is in greater contact with the wet hair (and any allergens) as a result of holding hair between the non-dominant ﬁngers while holding implements such as scissors in the dominant hand.

Figure 6.66 Allergic contact dermatitis to rubber. (a) The patient has developed an eczematous eruption on the thighs at the contact point of the elastic support band of the stocking. The classic rubber allergens are mercaptobenzothiazole, carba mix, and thiuram. (b) Elastic dermatitis to socks. Note the tremendous reaction to the elasticated portion of sports socks.

Figure. 6.67 Nickel dermatitis from earrings. Nickel allergy is very common in women. The earlobes become pruritic, inflamed, and eczematous. Licheniﬁcation may result from chronic rubbing. Other areas in contact with nickel-containing metal may react. When told they have an allergy, patients often protest, saying they have used the item for years without trouble. However, this is the typical story; usually it is only after years of exposure that the patient develops the allergy.

Figure. 6.68 Allergic contact dermatitis. (a) The cause of this eczematous rash was not obvious until (b) the patient put on his glasses.

Figure. 6.69 Nickel allergy. (a) Patch testing in this patient showed a nickel allergy. Three of her keys tested positive to dimethylglyoxime. Changing keys greatly improved the eruption. (b) This patient with an allergic sensitivity to nickel has developed a reaction on the lower abdomen to the inner metal fastener of jeans. (c) This patient developed a reaction at the site of contact with a safety pin.

Figure. 6.70 Nail polish allergy. (a) Note the streaky pattern of erythema on the neck. Material on the nails is not infrequently carried to the neck and face by the hands. (b) A periorbital eczematous dermatitis in a woman is not infrequently caused by allergy to material on the nails. Patch testing is usually in order, along with removal of all nail coatings. (Courtesy of Michael O. Murphy, M.D.)

Figure. 6.71 Airborne allergic contact dermatitis. (a) The pattern of airborne allergic contact dermatitis may resemble a photodistribution, in that it affects the exposed areas. However, areas typically spared UV exposure, such as the upper eyelids and the anterior neck, are usually affected by airborne contact dermatitis. (b) Airborne allergic contact dermatitis to balsam. Note the involvement of the anterior neck, which would not be seen in a photodistributed dermatitis. Also, the creases are involved, suggesting an airborne dust.

Figure. 6.72 Sebopsoriasis. Severe seborrheic dermatitis may resemble psoriasis. In such cases, the term sebopsoriasis is often used.

exposure to water, cold air, and irritants as much as possible. Gloves should be used as necessary to protect the hands (e.g. heavy-duty vinyl gloves for contact with water or when handling fruits or vegetables, cotton gloves for dry housework, and leather gloves for outdoor work). Wash the gloves, not the hands!
A topical steroid ointment morning and night is helpful for the erythema and itch, usually medium- to high-potency for the palms and low to medium for the ﬁnger webs or dorsum. Occlusion may be added if needed. Some patients prefer a cream, especially during the day. Frequent emolliation with a heavy cream or ointment is critically important. Because of their high water content, lotions are less effective. A hand cream should be carried conveniently for frequent use during the day, especially after water exposure and hand washing. If there is signiﬁcant roughness, ammonium lactate (12% lotion) combined with a potent steroid cream can help.
Painful ﬁssures may be occluded overnight with an antibiotic ointment if infection is a consideration. Oral antibiotics (e.g. erythromycin for 7 days) may be helpful, especially when ﬁssures or other signs of bacterial infection occur. Sometimes, treatment-resistant hand dermatitis, even without overt signs of bacterial infection, will respond to oral antibiotics.

Allergic contact dermatitis
Etiology and pathogenesis
Allergic contact dermatitis occurs through an allergic mechanism in which a topically applied allergen incites an allergic response. A variety of allergens may be implicated (Figs 6.45–6.52). Table 6.5 lists the most common allergens and their most likely source. When faced with a patient with an eczematous or even vesicular eruption, the possibility of allergic contact dermatitis should be considered (Fig. 6.53).
When cutaneous allergy is suspected, patch testing may be helpful (Figs 6.54–6.55). A standard tray of allergens, and, if necessary, selected allergens based on the history of exposure, are applied to the back for 48h. Conventionally, readings are performed at 48 h, and a second reading after a further 1–3 days is useful, as some tests may produce a delayed positive reaction. Unfortunately, the standard patch test trays available in the USA are becoming more and more inadequate at ﬁnding most clinically relevant contact allergens. In one study, the US standard allergy patch test kit and the Thin-Layer Rapid Use Epicutaneous Test kit (TRUE Test) identiﬁed less than a third of patients with allergic contact dermatitis. Oftentimes, the testing must include over 80–100 allergens. Examples of allergens missed by standard trays are cocamidopropyl betaine (an ingredient in ‘no more tears’ shampoos that can cause a contact dermatitis on the forehead), bacitracin, and gold sodium thiosulfate (suspect in cases of woman allergic to gold jewelry).
In the UK and Europe, experts meet to determine the tests that are likely to be most appropriate for routine screening, as this may vary with the introduction of new chemicals; for example, increased use of new preservatives may be associated with a rise in the reports of contact allergy, while older agents may be used less often and therefore problems with allergy diminish. The current (2004) European series is known as the Extended European Standard Battery and contains 35 agents.

Clinical

Lesions are either eczematous (Fig.6.56), microvesicular, or frankly bullous. Lesions may be linear (Fig. 6.57) or in streaks (Fig. 6.58), and may be asymmetric depending on the allergen and the mechanism of exposure. Certain sites suggest certain

Fig. 6.73 Seborrheic dermatitis of the nasolabial fold. Redness and scale along the nasolabial fold is a classic sign of seborrheic dermatitis.

Figure. 6.74 Seborrheic dermatitis of the eyebrow. Note the redness and scale.

allergens (Figs 6.59–6.64). For example, the scalp (also the neck and face) are affected by black hair dye (Fig. 6.65); rubber causes problems with shoes, gloves, and elasticated garments (Figs 6.60 and 6.66); nickel affects several sites (Figs 6.67–6.69); and nail polish may be transferred to the head and neck (Fig. 6.70).

Differential diagnosis
A huge range of differential diagnoses may apply, depending on the site affected; full discussion of all possibilities would be impossible. The main eczematous disorders to consider are as follows.

•	Irritant contact dermatitis—this presents similarly, as discussed earlier.
•	Photosensitivity—this may mimic a contact dermatitis due to an airborne allergen, or one that is applied to exposed sites (e.g. a sunscreen or moisturizer). Sometimes, an allergen may cause a reaction only when also sun-exposed (photoallergic contact dermatitis). A combination of patch testing and photopatch testing (Ch. 17) may help to distinguish between these conditions and others, such as chronic actinic dermatitis.
•	Atopic dermatitis—AD may coexist; always consider contact

Figure. 6.75 Diffuse seborrheic dermatitis of the face. Seborrheic dermatitis is the most common cause of a red, scaly facial rash.

Figure. 6.76 Seborrheic dermatitis of the chest. Seborrheic dermatitis commonly occurs on the mid-chest of an adult man.

allergy if there is an odd pattern, new pattern, flare after a prolonged trouble-free period or related to a new occupation, or resistance to therapy (remember topical steroid allergy).

Treatment
Obviously, the offending agent should be identiﬁed and eliminated. If left untreated and exposure to the allergen is removed, allergic contact dermatitis will run a 2–3-week course. If limited in scope and sufﬁciently severe, a potent topical steroid is appropriate. Lesser strengths are often not sufﬁcient. For widespread disease, a systemic corticosteroid is sometimes used (e.g. prednisone

Figure. 6.77 Seborrheic dermatitis in a black patient. Note the scale and postinflammatory hypopigmentation.

1 mg/kg for several days and then tapered over 2–3 weeks). Shorter ‘pulses’ will usually lead to relapse. In chronic cases, where allergen avoidance is difﬁcult to achieve (e.g. some airborne contact dermatitis, as discussed later), treatment options are as for AD.

Airborne contact dermatitis
Etiology and pathogenesis
Allergens in the air can cause a dermatitis in the exposed areas of the face, neck, and arms. Causative agents include pollens, dust, ragweed, sawdust, airborne household sprays, animal hairs, occupational volatile chemicals, Compositae plants, epoxy resin, chrysanthemums, and glutaraldehyde (occupational). In India, airborne contact dermatitis to the weed Parthenium hysterophorus has become widespread.

Clinical
A dry, licheniﬁed, and rarely vesicular eruption occurs in the exposed areas.

Differential diagnosis

•	Atopic dermatitis may show a preference for the head and neck.
•	Photodermatitis of several types, including photodistributed drug eruptions, may appear similar; however, airborne contact allergy typically affects the upper eyelid and anterior neck under the chin, whereas these photoprotected areas are spared, at least in the early stages, in a photodistributed eruption (Fig. 6.71).

Treatment
The offending allergen should be identiﬁed and avoided. Topical steroids should be prescribed. Narrow-band UVB therapy can be very effective for difﬁcult cases.