Chapter 16: The Skin

How much cream?

On average, 30 g of cream will cover the body surface area of an adult. Ointments, despite being of a thicker consistency, do not penetrate into the deeper skin layers so readily, and the requirements are slightly less. Pastes are applied thickly, and the requirements are at least 3 to 4 times as great as for creams.

The ‘rule of nines’, used routinely to determine the percentage of body surface area affected by burns (Fig. 16.1), may be used also to calculate the amount of a topical preparation that needs to be prescribed.

For example:

• If 9% of the body surface area is affected by eczema, approximately 3 g of cream is required to cover it.

• Nine grams of cream is used per day if prescribed 3 times daily.

• A 50 g tube will last 5 or 6 days.

One gram of cream will cover an area approximately 10 cm × 10 cm, and this formula may be used for smaller lesions.

Some general rules

1. Use creams or lotions for acute rashes.

2. Use ointments for chronic scaling rashes.

3. A thin smear only is necessary.

4. On average, 30 g:

   • will cover an adult body once

   • will cover hands twice daily for 2 weeks

   • will cover a patchy rash twice daily for 1 week.

5. On average, 200 g will cover a quite severe rash twice daily for 2 weeks.

When a patient with severe sunburn presents early, the application of 1% hydrocortisone ointment or cream can reduce significantly the eventual severity of the burn. This has been proved experimentally by covering one-half of the burnt area with hydrocortisone and comparing the outcome with the untreated area.

The application can be repeated 2 to 3 hours after the initial application and then the next morning. The earlier the treatment is applied the better, as it may not be useful after 24 hours.

Hydrocortisone should be used for unblistered erythematous skin, and not used on broken skin.

There is evidence that our skin needs exposure to sunlight to provide a substantial dose of vitamin D. This is a preventive for osteoporosis. Hats and sunscreens prevent the natural synthesis of vitamin D in the body.

There should be a balance between receiving enough sunlight exposure to prevent vitamin D deficiency on one hand and receiving too much, predisposing to skin cancer, on the other (see Table 16.1). A simpler guideline for most geographical areas is to recommend exposure to the face, arms and hands of 15–30 minutes a day in all climates and up to 50 minutes a day in winter in temperate areas.

Ocular protection from UV light

The best protection from the harmful effects of strong UV light is from wraparound UV-absorbing sunglasses (Australian Standard AS/NZS 1067:2003 for sunglasses and fashion spectacles).

Some topical treatment regimens

Mild to moderate acne

1. Apply isotretinoin 0.05% gel or tretinoin 0.05% cream each night (especially if comedones).

2. If inadequate response after 6 weeks, add benzoyl peroxide 2.5% or 5% gel or cream once daily (in the morning). That is, after 6 weeks, maintenance treatment is:

   • isotretinoin 0.05% gel at night

   • benzoyl peroxide 2.5% or 5% mane.

   In more severe cases, add clindamycin 1% topically to benzoyl peroxide.

3. Maintain for 3 months and review.

For a large area of mild truncal acne, consider topical salicylic acid 3% in ethanol 70% once daily.

Clindamycin use

Use clindamycin HCl in alcohol. Apply to each comedone with fingertips twice daily.

• A ready clindamycin preparation is Clindatech^®.

• Clindamycin is particularly useful for pregnant women and those who cannot tolerate antibiotics or exfoliants.

Other topical alternatives are:

• erythromycin 2% gel

• azelaic acid lotion, apply bd

• adapalene 0.1% cream or gel, apply nocte

• tazarotene 0.1% cream, once nocte.

Oral antibiotics

Use if acne is resistant to topical agents. Doxycycline 100 mg day or minocycline 50–100 mg nocte for 4 weeks (or up to 10 weeks if slow response), then reduce according to response (e.g. doxycycline 50 mg for 6 weeks).

If tetracyclines not tolerated or contraindicated (e.g. in pregnancy) use erythromycin 250–500 mg (o) bd.

Facial scars

Injections of collagen can be used for the depressed facial scars from cystic acne.

• Keep the area dry.

• Change wet or soiled napkins often—highly absorbable disposable ones are good.

• Wash area gently with warm water and pat dry (do not rub).

• Avoid excessive bathing and soap.

• Avoid powders and plastic pants.

• Use emollients to keep skin lubricated, e.g. zinc oxide and castor oil cream.

• Standard treatment for persistent or widespread rash is 1% hydrocortisone with nystatin or clotrimazole cream, e.g. Hydrozole^® (qid after changes)—you can get separate steroid and antifungal creams and mix before application. Avoid stronger steroid preparations. Consider continuing the antifungal cream for another 7 days.

If seborrhoeic dermatitis: 1% hydrocortisone and ketoconazole ointment.

Tip: If rash is resistant and ulcerated, add Orabase^® ointment bd or tds. Another tip is to add petroleum jelly to the above medication in equal parts—this can be used for a ‘normal’ nappy rash since it promotes longer action. Another strategy is to give oral zinc.

Note importance of good education.

Medication

Mild atopic dermatitis

• Avoid soap. Use soap substitutes, such as emulsifying ointment or a bland bath oil in the bath and a cleansing bar, e.g. Dermaveen.

• Emollients (choose from):

  • Ego skin cream

  • emulsifying ointment with 1% glycerol

  • sorbolene or sorbolene with 10% glycerol, e.g. Hydraderm^®

  • paraffin creams (e.g. Dermeze^®) (good in infants)

  • bath oils, e.g. Alpha-Keri, QV, Dermaveen

  • moisturising lotions (e.g. QV) in summer.

• 1% hydrocortisone (if not responding to above). Use twice daily (if poor response).

Moderate atopic dermatitis

• As for mild eczema.

• Topical corticosteroids (twice daily):

  • vital for active areas

  • moderate strength, e.g. fluorinated, to trunk, scalp and limbs

  • weaker strength, e.g. 1% hydrocortisone, to face and flexures

  • use in cyclic fashion for chronic cases (e.g. 10 days on, 4 days off).

• Non-steroidal alternative: pimecrolimus (Elidel^®) cream bd; best used when eczema flares, then cease.

• Oral antihistamines at night for itch.

Severe dermatitis

• As for mild and moderate eczema.

• Potent topical corticosteroids to worst areas (consider occlusive dressings).

• Consider hospitalisation.

• Systemic corticosteroids (may be necessary but rarely used).

• Allergy assessment if unresponsive.

Weeping dermatitis (an acute phase)

This often has crusts due to exudate. Burrow’s solution diluted to 1:20 or 1:10 can be used to soak the affected areas.

Tip for children

If severe eczema is not responding to topical treatment, try evening primrose oil and/or oral zinc.

General tips

• Rehydration is the single most important treatment strategy. Avoid soaps.

• Avoid creams (tend to sting and less potent).

• Topical steroids:

  • potent steroids safe for short periods

  • intermittent rather than continuous use

  • replace with emollients when clear.

• Lotions rather than creams are best for moisturising.

• For dry scaly lesions, use ointments with or without occlusion.

General adjunctive therapy

• Tarbaths, e.g. Pinetarsol™ or Polytar^®.

• Tar shampoo (e.g. Polytar^®, Ionil-T^®).

• Sunlight (in moderation).

For chronic stable plaques on limbs or trunks

Topical steroids—potent ones preferred, or

Method A

• Apply dithranol 0.1% cream to affected area at night. Leave 20–30 minutes and then wash off under shower. Increase strength every 5 d to 1% (up to max. 2 hrs).

• Then apply topical fluorinated corticosteroid in the morning.

Combined method

• 

  Leave overnight (warn about dithranol stains—use old pyjamas and sheets). Review in 3 weeks, then gradually increase strength of dithranol to 0.25%, then 0.5%, then 1%.

  Can cut down frequency to 2 to 3 times per week. Shower in morning, and then apply topical fluorinated corticosteroid.

  Note: Dithranol tends to ‘burn’ skin.

• Don’t use dithranol on face, genitalia or flexures.

• A higher strength (0.25% to start) can be used for short contact therapy (30 minutes before shower).

Alternative method (adults only)

• Calcipotriol ointment—apply bd. Tends to irritate face and flexures; wash hands after use. Limit to 100 grams per week. Use for localised plaques. Can combine with a potent corticosteroid.

For milder stabilised plaques

• Egopsoryl TA™—apply bd or tds, or

• topical fluorinated corticosteroids.

For resistant plaques

• Topical fluorinated corticosteroids (II–III class) with occlusion.

• Intralesional injection of triamcinolone mixed (50:50) with LA or normal saline (see Fig. 3.21).

For failed topical therapy (options)—specialist case

• Refer for PUVA or other effective therapy.

• Acitretin—often used with UVB.

• Methotrexate—can have dramatic results.

• Biologicals, e.g. infliximab, etanercept.

Equipment

You will need:

• a scalpel blade

• glass slide and cover slip

• 20% potassium hydroxide (preferably in dimethyl sulfoxide)

• a microscope.

Method

1. Scrape skin from the active edge.

2. Scoop the scrapings onto the glass microscope slide.

3. Cover the sample with a drop of potassium hydroxide.

4. Cover this with a cover slip and press down gently.

5. Warm the slide and wait at least 5 minutes for ‘clearing’.

Microscopic examination

1. Examine at first under low power with reduced light.

2. When fungal hyphae are located, change to high power.

3. Use the fine focus to highlight the hyphae (Fig. 16.2).

Note: Some practice is necessary to recognise hyphae.

The most effective treatment of spider naevi for cosmetic reasons is to insert the fine tip of the electrocautery or the hyfrecator (diathermy) needle into the central papule and cauterise the vascular lesion.

No local anaesthetic is required.

Wood’s light examination is an important diagnostic aid for skin problems in general practice. It has other uses, such as examination of the eye after fluorescein staining. (New, low-cost, small ultraviolet light units called ‘the black light’ are available, e.g. the Radio Shack UV scanner or fluorescent lantern.)

Method

Simply hold the ultraviolet light unit above the area for investigation in a dark room.

Limitations of Wood’s light in diagnosis

Not all cases of tinea capitis fluoresce, because some species that cause the condition do not produce porphyrins as a byproduct. See Table 16.2 for a list of the skin conditions that do fluoresce.

Porphyrins wash off with soap and water, and a negative result may occur in a patient who has shampooed the hair within 20 hours of presentation. Consequently, a negative Wood’s light reading may be misleading. The appropriate way of confirming the clinical diagnosis is to send specimens of hair and skin for microscopy and culture.

Note: Wood’s light examination can also be used for eye diagnosis after instilling fluorescein.

The self-application of creams or ointments to relatively inaccessible areas such as the back, especially in the elderly, can be difficult. One method is to acquire an old-fashioned dish mop, give it a ‘crew cut’ and use this to apply the preparations.

Patients with florid hand dermatitis handicapped by a slow response to topical corticosteroids can be boosted by the application of a surgical glove to wear for 60 minutes after applying the cream or ointment or even overnight if tolerated. This leads to less frequent application.

Precautions

• Think Raynaud.

• Protect from trauma and secondary infection.

• Do not rub or massage injured tissues.

• Do not apply heat or ice.

Physical treatment

• Elevate affected part.

• Warm gradually to room temperature.

Drug Rx

• Apply glyceryl trinitrate vasodilator spray or ointment or patch, e.g. Nitro-Bid^® ointment (use plastic gloves and wash hands for ointment).

Other Rx

• Rum at night (worth a try).

• Nifedipine 20 mg bd or CR 30 mg once daily.

Herpes labialis (classical cold sores)

The objective is to limit the size and intensity of the lesions.

Topical treatment

At the first sensation of the development of a cold sore:

• apply an ice cube to the site for up to 5 minutes every 60 minutes (for first 12 hours)

  or

  saturated solution of menthol in SVR.

• topical applications include:

  • idoxuridine 0.5% preparations (Herplex D^® liquifilm, Stoxil^® topical, Virasolve^®) applied hourly,

    or

  • povidone-iodine 10% cold sore paint: apply on swab sticks 4 times a day until disappearance,

    or

  • acyclovir 5% cream (Zovirax^®), 5 times daily for 4 days.

Oral treatment

Acyclovir or famciclovir or valaciclovir for 5 to 10 days or until resolution (reserve for immunocompromised patients and severe cases).

Prevention

If exposure to the sun precipitates the cold sore, use a 30+ or 50+ sun protection lip balm, ointment or solarstick. Zinc sulfate solution can be applied once a week for recurrences. Oral acyclovir 200–400 mg bd or similar agent (6 months) can be used for severe and frequent recurrences (> six per year).

Genital herpes: Antimicrobial therapy

Topical treatment

The proven most effective topical therapy is topical acyclovir (not the ophthalmic preparation).

Alternatives:

• 10% povidone-iodine (Betadine^®) cold sore paint on swab sticks for several days.

Pain relief can be provided in some patients with 2% topical lidocaine, but be cautious of hypersensitivity.

Saline baths and analgesics are advisable.

Oral treatment

Acyclovir for the first episode of primary genital herpes (preferably within 24 hours of onset).

Dosage: 400 mg 3 times a day for 5 to 7 days or until resolution of infection.

Famciclovir or valaciclovir can be given bd for 5 to 10 days.

This appears to reduce the duration of the lesions from 14 days to 5 to 7 days. These drugs are not usually used for recurrent episodes, which last only 5 to 7 days. Very frequent recurrences (six or more attacks in 6 months) benefit from low doses of these agents for 6 months (200 mg 2 to 3 times per day).

Topical treatment

For the rash, use a drying lotion such as menthol in flexible collodion. Acyclovir ointment can be used but it tends to sting.

Oral medication

1. Analgesics, e.g. paracetamol, codeine or aspirin.

2. Guanine analogue antiviral therapy for:

   • all immunocompromised patients

   • any patient, provided rash present < 72 hours (especially those over 60 years)

   • ophthalmic zoster (evidence to reduce—reduces scarring and pain but not neuralgia)

   • severe acute pain.

Drugs and dosage

• Acyclovir 800 mg 5 times daily for 7 days

  or

• famciclovir 250 mg 8 hourly for 7 days

  or

• valaciclovir 1000 mg 8 hourly for 7 days.

Post-herpetic neuralgia

Some treatment options are:

1. Topical capsaicin (Capsig) cream. Apply the cream to the affected area 3 to 4 times a day. Give ice massage 20 minutes beforehand.

2. Oral: paracetamol is first line. Second line is a tricyclic antidepressant, gabapentin or pregabalin.

3. TENS as often as necessary, e.g. 16 hours/day for 2 weeks, plus antidepressants.

4. Excision of painful skin scar. If the neuralgia of 4 months or more is localised to a favourable area of skin, a most effective treatment is to excise the affected area, bearing in mind that the scar tends to follow a linear strip of skin. This method is clearly unsuitable for a large area.

Method

1. Mark out the painful area of the skin.

2. Incise it with its subcutaneous fat, using an elongated elliptical excision (Fig. 16.3).

3. Close the wound with a subcuticular suture or interrupted sutures.

Reactions to the following have been reported:

• spirit preparation

• paper-based ‘hypoallergenic’ tape.