• Dermatitis refers to a group of itchy inflammatory conditions characterized by epidermal changes.
• The terms dermatitis and eczema are often used interchangeably.

Relationship with Eczema:

• ALL eczema is a dermatitis
• BUT not all dermatitis is eczema.

• Dermatitis = any cause of skin inflammation affecting the epidermis.
• Eczema = derived from the Greek word for “to boil or bubble over”, which pathologically manifests as oedema within the epidermis (called spongiosis).

Classification:

Dermatitis can be categorized based on various factors:

1. Cause:
   • Allergic contact dermatitis
   • Photosensitive dermatitis
2. Clinical Appearance:
   • Discoid dermatitis/Nummular dermatitis
     • characterized by coin-shaped patches of irritated skin.
     • It often occurs after skin injuries, such as insect bites or abrasions, and tends to be more prevalent in winter.
   • Hyperkeratotic dermatitis
   • Pompholyx/Dyshidrotic eczema
     • primarily affects the palms of the hands and soles of the feet.
     • It is characterized by small, itchy blisters and can be triggered by factors like stress or exposure to certain metals.
3. Site of Predilection:
   • Hand dermatitis
   • Eyelid dermatitis
   • Lower leg dermatitis
4. Combined Factors:
   • Various factors may act as triggers together (allergic, irritant, and endogenous factors).

Epidemiology of Dermatitis

• Dermatitis is common, affecting about one in every five persons at some stage in their life.
• Different types are more frequent at different life stages.
  • Atopic dermatitis and pityriasis alba are more common in children
  • Hand eczema is more common in young and middle-aged adults
  • Venous or gravitational eczema, asteatotic dermatitis, and nummular eczema are more common in middle and older age groups. 

Clinical Features of Dermatitis

• Dermatitis may be acute or chronic, with varying appearances.
• Acute dermatitis shows
  • redness
  • swelling
  • vesiculation
  • oozing.
• Chronic eczema presents with
  • skin thickening
  • hyperkeratosis
  • excoriation.

Racial Variation in Clinical Features

• Redness may be more challenging to appreciate in darker skin types.
• Post-inflammatory hypo- and hyperpigmentation are more frequent in darker skin types.

Types of Dermatitis and Their Causes

Exogenous Dermatitis:

• Allergic contact dermatitis — due to immune sensitisation of an individual to an allergen, often at even low concentration, such as nickel, hair dye, rubber, or perfumes; identified by patch testing.
• Irritant contact dermatitis — will occur in anyone exposed to an irritant at sufficient concentration for long enough; irritants include soaps, detergents, organic solvents, degreasing agents, abrasives, desiccants, dust, urine, and even water
• Photosensitive dermatitis — triggered by light or UV radiation
• Post-traumatic dermatitis — due to physical injuries such as abrasions, burns, or surgery (eg, autonomic denervation dermatitis)
• Dermatitis induced by local skin infections such as bacterial, fungal, and viral e.g. molluscum contagiosum and HTLV-1 disease
• Drug-induced dermatitis.

Endogenous Dermatitis:

Atopic dermatitis — a common form of dermatitis occurring in children and adults, and often occurring in families with a background of asthma and hay fever
Seborrhoeic dermatitis — common chronic eczema affecting the face, scalp, ears and major flexures, due to a reaction to yeasts that colonise the skin
Discoid (nummular) dermatitis — coin-shaped patches of dermatitis usually affecting the limbs
Lichen simplex — chronic dermatitis that thickens due to perpetual scratching
Pityriasis alba — pale patches of dermatitis affecting the cheeks
Hand dermatitis — internal, external irritants and allergic factors may all play a part even in a single individual
Eyelid dermatitis — again, often of mixed cause
Otitis externa — dermatitis affecting the ear canal and the pinna
Venous or gravitational dermatitis — dermatitis due to malfunction of the lower leg vein valves
Juvenile plantar dermatitis — a glazed and fissured forefoot eczema occurring in children
Metabolic dermatitis — seen in – obesity – hypertension – dyslipidaemia – insulin resistance.
Chronic superficial scaly dermatitis — finger-shaped patches of eczema occurring on the trunk
Asteatotic dermatitis — crazy-paving shaped dermatitis due to degreasing of the skin from excessive bathing and soap use on the legs in the elderly
Halo dermatitis or Meyerson naevus — this can surround a benign mole
Erythrodermic dermatitis — severe dermatitis when more than 80% of the skin is affected.

Differential Diagnosis of Dermatitis

• Bacterial and fungal infections
• Connective tissue diseases
• Rosacea
• Blistering diseases
• Skin tumors
• Cutaneous T-cell lymphoma

Investigation and Treatment of Dermatitis

Investigation:

• Detailed history and examination
• Skin scraping
• swab
• patch testing
• light testing
• skin biopsy
• blood tests

Treatment:

1. General Principles:
   • Allergen and irritant identification and avoidance
   • Personal protective equipment for specific cases
   • Exacerbated by heat, prickle (wool, nylon, seams, labels) and dryness
2. Avoid triggers:
   • Avoid soap
   • Avoid hot baths
   • Avoid “prickly” clothes
   • Avoid scratching
3. Moisturisers:
   • Dermeze (50% soft/ 50% liquid paraffin oil)
   • 4-­6x a day if needed
   • Applied over CS if using
4. Topical Therapies:
   • Emollients, potassium permanganate soaks, paste bandages
   • topical steroids
     • Hydrocortisone 0.5-­1% on face BD
     • Elocon on body OD
   • Calcineurin inhibitors, JAK inhibitors’
5. Physical Therapies:
   • Ultraviolet B and Psoralens UVA (PUVA)
6. Systemic Agents:
   • Antihistamines (for itch)
   • antibiotics (secondary infection)
   • antivirals
   • Immunosuppressive therapies (methotrexate, azathioprine, ciclosporin)
   • Biological therapies (dupilumab, tralokinumab, lebrikizumab, nemolizumab)
   • Oral small molecules (baricitinib, upadacitinib, abrocitanib) for moderate/severe atopic dermatitis.

• Additional:
  • Cold compresses and wet dressings
  • Diet: breastfeed as long as possible, consider elimination  diet

Contact dermatitis

• caused by allergens that provoke an allergic skin reaction (where most other peole can handle the chemicals without undue effect.) 
• causes:
  • nickel (jewellery, jeans, keys, coins)
  • fragrances
  • plants, dyes, chemicals, latex etc
• features:
  • dermatitis isolated to site affected but can spread through contact of fingers
• dx: if in doubt refer to dermatologist for patch testing
• mx:
  1. key is avoiding contact so much know allergen! 
  2. Avoid soap (only wash with water) + topical corticosteroid
  3. if severe short course of oral pred (starting 25-50mg for adult for 1-2 wks then reduce over 1-2wks) +/- oral abx for 2° infection

Nummular/discoid eczema

scattered, well-defined, coin-shaped and coin-sized plaques of eczema. Discoid eczema is also called nummular dermatitis

The eruption can be precipitated by:

• A localised injury such as scratch, insect bite or thermal burn
• Impetigo or wound infection
• Contact dermatitis
• Dry skin
• Varicose veins (varicose eczema)  

Differentials : annular skin eruptions including 

• tinea corporis
• plaque psoriasis

Management

• Protect the skin from injury.=  irritated by friction, detergents, solvents, other chemicals, or excessive water.
• soap substitutes and moisturising cream
• Avoid allergens
• Topical steroids – twice daily for 2–4 weeks
• Antibiotics
• Oral antihistamines
• Ultraviolet radiation (UV) treatment

Atopic dermatitis

– criteria for dx

• Itch
• Typical morphology
  • distribution (changes; baby = cheeks, face, folds of neck, scalp + extensor surfaces 🡪 child flexures of limb + groin 🡪 adult groin, ext hand, feet, neck)
• Dry skin
• Hx of atopy (or family hx -allergic rhinitis, asthma, eczema, skin sensitivities & urticarial)
• Chronic relapsing dermatitis

triggers

• dust mite (common), extremes tempt, sweating, sand pits, soap/frequent washing, pools, infection, stress, irritants (clothing, detergents), foods, scratching/rubbing, perfumes

prognosis 

• most children ‘grow out of it’ as the function of their oil & sweat glands matures. Lichenification can occur w chronic atopic dermatitis. 

• 60% normal skin at 6 yrs
• 90% normal skin by puberty

treatment = 

• General advise = avoid soap + perfumed products (use low ph ie: dermaveen, hamiltons, qv, cetaphil) & apply emollient (sorbolene w 10% glycerol, paraffin creams – dermeze, qv moisturizing cream) immediately after bathing. Older children should have short, tepid showers. Avoid overheating/changes in t°. Wear loose clothing preferably cotton
• Consider dust mite strategies
  •  dust mite covers (premium grade) for bedding; wash linen in hot water >55°, consider replacing fabric on chairs + carpet
• Anti histamines
  • can be given at night for itch, if used the sedating type is recommended. 
  • Ie: promethazine (phenergen) safe if >12yrs, can be used for short term use in children younger
• Antibiotics
  • pt’s at risk of 2° infection with staph, try to prevent with anti-septic wash 
  • White king bleach (4%) to cool bath water at 12mls per 10l, wash scalp+face
  • Topical = mupirocin 2% (bactroban) or systemic = flucloxacillin or cephalexin

• Anti-virals
  • oral acyclovir as risk hsv 🡪 vesicles & ‘punched out lesions’ & pain
• Steroids =
  • Face & flexures = 1% hydrocortisone (sigmacort or dermaid) once or twice daily until dermatitis settles then back to emollients. If not effective 🡪 methylprednisolone 0.1% (advantan) once daily until dermatitis settles, usually 7 days
    • Alternative for face is a calcineurin inhibitor (ie: pimecrolimus = elidel)
  • Treatment elsewhere on = moderately potent corticosteroid once to twice daily until settled, usually 7 – 14 days
    • Betamethasone valerate 0.02% (celestone) or 0.05% (betnovate ½)
    • Methlyprednisolone (advantan)
    • Triamcinolone (aristocort)
  • For lichen simplex or thick skin (palm or sole of foot) = potent or very potent corticosteroid once daily until settles, can take up to 3 weeks
    • Betamethasone diproprionate (diprosone)
    • Betamethasone valerate 0.1% (betnovate)
    • Mometasone 0.1% (elocon)
• Nb: if severe dermatitis may need occlusive dressings +/- hosp admission. Apply moisturizer and/or corticosteroid then apply wet dressing followed by dry. Left on overnight or changed 4x during day. Inappropriate use leads to folliculitis, infection, maceration or excessive dryness. A wet compress can be applied to affected area for 5-10mins to relieve itch, moisturize after. 
• advise on steroids
  • use cream base if weeping, use ointment base if dry or lichenification & lotion based if hairy areas
  • use steroid for 7-14d & ask to return for review if doesn’t settle in expected timeframe
  • if flares can have short term use 7-14days then switch to emollient
  • if moderate or more potent steroid one daily administration is usually enough
• staph eradication
  • quarter fill bath w water + add 45ml (3 tbls) of household bleach (ie: white king.
  • Soak in bath for 5 minutes but don’t immerse face
  • Rinse skin in fresh water & pat dry using old towels to avoid bleaching coloured towels.
  •  Immediately apply prescribed creams + moisturizer. Repeat twice a week or as suggested by your doctor.

Ichthyosis vulgaris

excessive dry, scaly skin  

It is the most common form of the inherited ichthyoses

• Treatments
  • Keep skin hydrated
    • Apply emollients with high lipid content, such as lanolin cream (a sebum-like substance derived from wool-bearing animals).
• Treatments to reduce scale
  • Bathe in salt water.
  • Apply creams or lotions containing salicylic acid, glycolic acid, lactic acid or urea to exfoliate and moisturise skin. These may irritate active eczema.
  • Oral retinoids such as acitretin or isotretinoin can be prescribed in severe cases.

Pityriasis alba 

• Pityriasis alba is a low-grade type of eczema/dermatitis mainly seen in children 3-16 years.
• form of subacute atopic dermatitis
• very common mild condition, worse in summer (b/c won’t tan) & dark skinned children
• self limiting and will clear up in months, sometimes years
• diagnosis
  • rule out other causes of pigmentation
    • Wood lamp examination: the hypopigmentation of pityriasis alba does not enhance, and there is no fluorescence
    • Scrapings for mycology: microscopy and fungal culture are negative in pityriasis alba
    • Skin biopsy: biopsy is rarely required, but may reveal mildly spongiotic dermatitis and reduction in melanin.
• mx: non-soap cleanser, emollients. Hydrocortisone rarely needed or pimecrolimus

Treatment

No treatment is necessary for asymptomatic pityriasis alba.

• A moisturising cream may improve the dry appearance.
• A mild topical steroid (0.5-1% hydrocortisone) may reduce redness and itch if present.
• Calcineurin inhibitors (pimecrolimus cream and tacrolimus ointment) may be as effective as hydrocortisone and have been reported to speed recovery of skin colour.

Asteatotic dermatitis

A “Cracked Porcelain” Appearance

Caused by water loss from the stratum corneum. 

This occurs because of a breakdown of the skin barrier due to genetic predisposition and injury by environmental factors. These include:

• Low humidity (winter, desert, high altitude, travel, use of dehumidifier or fan heater)
• Excessive bathing especially using soaps and detergents

Who gets asteatotic eczema? – Asteatotic eczema can occur in anyone with very dry skin.

• It most often affects older people.
• It is also a complication of inherited and acquired forms of ichthyosis.
• Systemic causes include underactive thyroid (myxoedema), malnutrition (zinc and fatty acid deficiencies), severe weight loss and lymphoma.
• Drugs can cause asteatotic eczema, particularly retinoids (acitretin, isotretinoin), diuretics and protein kinase inhibitors.

treatment.

• Consider factors that have caused dry skin: bathe less frequently, use a cream cleanser instead of soap, do not expose skin to direct heat.
• Apply thick emollients and moisturisers such as petroleum jelly/petrolatum or oily cream several times daily — after a few days, thinner ones such as non-ionic cream should be adequate.
• Apply mild topical steroid cream or ointment to reddened skin for a few days; hydrocortisone cream or ointment is often sufficient.
• A more potent topical steroid may be necessary if the eczema is severe.