Eczema (a.k.a. dermatitis)

Types of eczema:

Are many types. The 3 main ones are listed below:

• Atopic dermatitis
• Contact dermatitis
• Seborrhoeic dermatitis

General clinical features – dermatitis:

• Erythema
• Papules
• Vesicles
• Excoriation/pruritus
• Secondary infection

Atopic dermatitis

Aetiology:

• Unknown

• Strong familial tendency
• If one parent has atopic disease, the risk for a child of developing eczema is about 20-30%
• If both parents have atopic eczema, the risk is >50%

Exacerbating factors:

Exacerbating factors are not necessarily allergens

• Strong detergents, chemicals
• Woollen clothes
• Severe anxiety, stress
• Cat/dog fur (possibly by both allergic and irritant mechanisms)

Specific clinical features:

• Commonest sites are:
• Front of elbows/ankles
• Back of knees
• Around the neck

Investigations:

• Diagnosis is usually clinical
• Atopy is characterised by high serum IgE levels or high specific IgE levels to certain ingested or inhaled antigens:
• Can be tested by radio-immunoabsorbent assay (RAST tests) of blood
• Skin-prick testing

Prognosis:

• Vast majority of children with early-onset atopic eczema will improve spontaneously and ‘clear’ before the teenage years, 50% being clear by the age of 6
• If the onset is late in childhood or in adulthood, the disorder follows a more chronic remitting/relapsing course

Treatment:

General measures:

• Avoid known irritants (especially soaps or furry animals)
• Not getting too hot

Topical therapies:

• Are sufficient to control atopic eczema in most people and the following ‘triple’ combination often helps:
• Topical steroid bds when needed
• Emollient frequently
• Bath oil (e.g. oilatum or balneum) and soap substitute (e.g. aqueous cream)

It should be noted that topical steroids can be safely prescribed for long-term, intermittent, use.

Antibiotics:

• Are needed for bacterial infection
• Usually given orally for 7-10 days
• E.g. flucloxacillin (500mg tds) is effective against Staphylococcus
• E.g. penicillin V (500mg tds) acts against Streptococcus
• Erythromycin (500mg tds) is useful if there is allergy to penicillin

Contact and irritant dermatitis

Overview:

• One may suspect this if the eczema is in an unusual or localised distribution, especially if there is no personal or family history of atopic disease
• A history of an exacerbation of eczema at the workplace is also suggestive

This can happen by 2 mechanisms:

• Direct irritation
• Allergic reaction (type IV delayed hypersensitivity)

A detailed history about occupation, hobbies, cosmetic products and clothing and contact with chemicals is necessary

Irritant eczema:

• Can occur in any individual
• It often occurs on the hands after repeated exposures to irritants such as detergents, soaps or bleach
• It is, therefore, common in housewives, cleaners, hairdressers, mechanics and nurses

Contact eczema:

• Occurs after repeated exposure to a chemical substance but only in those people who are susceptible to develop an allergic reaction
• Common (up to 4% of the population)
• Most common culprits are:
• Nickel (costume jewellery, buckles)
• Latex
• Chromate (in cement)

Treatment:

• As for atopic eczema, as well as strict avoidance of any causative agent
• This may involve the wearing of protective clothing (e.g. gloves) or may involve a change of occupation or hobby

Seborrhoeic eczema

There is some evidence that the yeast Pityrosporum ovale is important and may act as an ‘antigenic drive’ to produce the characteristic inflammation and scaling of seborrhoeic eczema. The condition is more common in Parkinsonism as well as HIV.

Clinical features:

3 age groups are affected:

In childhood:

• Common
• Presents in the first few months of life as ‘cradle cap’ in most babies
• May be, in part, due to the effect of maternal androgens on infant sebaceous glands
• Yellowish, greasy, thick crusts are seen on the scalp
• A more widespread erythematous scaly rash can be seen over the trunk, especially affecting the nappy area
• Unlike atopic eczema, the child is normally unbothered as there is little associated pruritus
• Usually improves spontaneously after a few weeks

In young adults:

• Males > females
• Occurs in 1-3% of the population
• Presents as an erythematous scaling:
• Along the sides of the nose
• In the eyebrows
• Around the eyes
• Extending into the scalp (giving rise to marked dandruff)
• May affect the skin over the sternum and of the glans penis

In elderly people:

• Can be quite severe and progress to involve large areas of the body
• May even cause erythroderma

Treatment:

• The treatment is suppressive rather than curative
• Combination of:
• Mild steroid ointment (e.g. 1% hydrocortisone bds)
• Topical antifungal cream (e.g. miconazole cream bds)

• Ketoconazole shampoo and arachis oil are useful for the scalp