Section 1: Introduction -- The Prescription That Goes Wrong on the Skin

A 34-year-old woman in Kingston attends a health centre with a rash in the groin. The rash is erythematous, with a scaly border and central clearing. It is tinea cruris -- a dermatophyte fungal infection. She is prescribed betamethasone 0.1% cream.

Betamethasone is a potent topical corticosteroid. Applied to tinea cruris, it does not treat the infection -- it suppresses the inflammatory response that makes the infection visible. The rash appears to improve. The fungal infection deepens. When the corticosteroid is stopped, the infection returns -- often more widespread, more resistant to treatment, and with skin changes from the steroid itself.

This is one of the most common prescribing errors in Caribbean dermatological practice. The rash that appears after a steroid "worked" briefly and then "came back" is frequently tinea that was masked and amplified. The corticosteroid-modified tinea (also called tinea incognito) can spread across the groin, buttocks, and inner thighs while appearing atypical -- without the classic scaly border -- because the inflammatory response has been suppressed.

Caribbean skin prescribing has three specific challenges that this report addresses in full:

The steroid-for-everything reflex. Topical corticosteroids are effective for a wide range of inflammatory skin conditions. They are also frequently applied to conditions they do not treat and, in some cases, actively worsen: tinea, bacterial skin infections, rosacea, and perioral dermatitis.

Chronic steroid misuse. Potent topical corticosteroids applied daily for months or years -- particularly on the face or in skin folds -- cause skin atrophy, telangiectasia, striae, perioral dermatitis, and steroid rosacea. They can cause adrenal suppression, particularly in children and in adults applying large quantities to thin skin areas.

Bleaching agents and skin lightening products. Skin lightening is practised across the Caribbean and is a significant public health concern. Products containing hydroquinone (legal in low concentrations in some territories; banned in others), mercury compounds (illegal everywhere but found in imported products), corticosteroids (misused for their bleaching-adjacent pigment-reducing effects), and tretinoin are used daily by a substantial proportion of Caribbean women, and some men. The health risks -- mercury toxicity, ochronosis from high-dose hydroquinone, corticosteroid-induced skin damage, and systemic absorption -- require clinician awareness.

Section 2: Topical Corticosteroids -- The Potency Ladder

2.1 Potency classification

Topical corticosteroids are classified into four potency groups. The clinical importance of this classification is that the choice of potency must match the condition being treated and the site of application. Using a potent corticosteroid on a mild condition or on a high-absorption site causes harm. Using a mild corticosteroid on severe psoriasis or lichen planus produces no benefit.

2.2 Site of application and absorption

Corticosteroid absorption varies markedly by anatomical site. The same drug at the same potency produces different systemic exposure depending on where it is applied:

The clinical implication: A potent corticosteroid applied to the face or genitals produces substantially higher systemic exposure than the same product applied to the palm. This matters for: - Adrenal suppression risk (particularly in children and with large surface area application) - Skin atrophy risk (highest on thin skin areas: face, genitals, skin folds) - Corticosteroid-induced glaucoma (periocular application)

2.3 Adverse effects of topical corticosteroid misuse

2.4 The conditions where topical corticosteroids are NOT indicated

• Tinea (ringworm, athlete's foot, tinea cruris) -- antifungal treatment required; corticosteroids worsen the infection
• Acne vulgaris -- corticosteroids aggravate acne
• Rosacea -- corticosteroids produce initial improvement then rebound worsening; cause steroid rosacea
• Bacterial skin infections (impetigo, infected eczema requiring antibiotic) -- corticosteroid alone is inadequate; combined antibiotic-steroid preparations are appropriate when both inflammation and infection are present
• Molluscum contagiosum -- viral; corticosteroids do not treat it
• Scabies -- corticosteroids suppress the itch but do not treat the infestation

Section 3: Antifungal Prescribing -- Getting the Diagnosis Right First

3.1 Tinea vs eczema vs psoriasis -- the diagnostic challenge

The most consequential clinical decision in skin prescribing is whether a rash is inflammatory (eczema, psoriasis, seborrhoeic dermatitis) or fungal (tinea). Corticosteroids are the correct treatment for the former and worsen the latter. A brief diagnostic framework:

Where diagnostic uncertainty exists, a skin scraping for KOH microscopy (where available) or empirical treatment with a topical antifungal (safe, will not worsen eczema significantly) is preferable to empirical corticosteroid treatment (which will worsen tinea significantly).

3.2 Topical antifungals

3.3 Systemic antifungals -- when topical treatment is insufficient

Systemic antifungals are required when: - Tinea capitis (scalp ringworm) -- topical antifungals do not penetrate the hair follicle adequately - Extensive tinea corporis or cruris not responding to topical treatment - Onychomycosis (nail infection) -- terbinafine or itraconazole orally for 6-12 weeks (nails) - Immunocompromised patients with cutaneous fungal infections

Drug interactions (Report 12): - Fluconazole (CYP2C9 and CYP3A4 inhibitor): warfarin INR rises, glibenclamide hypoglycaemia risk - Itraconazole (CYP3A4 inhibitor): amlodipine, simvastatin, carbamazepine levels rise - Terbinafine (CYP2D6 inhibitor): reduces tramadol and codeine activation; reduces metoprolol clearance

Section 4: The Bleaching Problem -- A Caribbean Public Health Issue

4.1 The scale of skin lightening in the Caribbean

Skin lightening is practised widely across the Caribbean. Surveys across Jamaica, Trinidad, and other territories report use rates of 25-50% among women. Products used range from medically supervised hydroquinone formulations to illegally manufactured creams containing mercury and high-potency corticosteroids.

The drivers are cultural and social -- documented associations between lighter skin tone and social advantage in various Caribbean contexts -- and the clinical consequences are being seen in dermatology clinics across the region.

4.2 Hydroquinone

Hydroquinone is a melanin synthesis inhibitor (inhibits tyrosinase). It is effective for hyperpigmentation and post-inflammatory hyperpigmentation. It is the only medically approved skin lightening agent in most jurisdictions.

Approved use: 2% (over the counter in some territories), 4% (prescription only), for post-inflammatory hyperpigmentation, melasma, and solar lentigines. Courses of 3-6 months, with concurrent sun protection.

Risks of unregulated use: - Ochronosis: Paradoxical darkening of skin with long-term high-concentration use. Characterised by blue-black discolouration of the treated areas. Irreversible. More common in darker skin phototypes. Associated with prolonged use of high concentrations (above 4%) in products without medical supervision. - Contact sensitisation: Hydroquinone is a common sensitiser; allergic contact dermatitis can develop with continued exposure. - Systemic absorption: With extensive application, systemic absorption occurs. The systemic toxicity of hydroquinone is not fully characterised but animal data suggests renal and hepatic effects.

4.3 Mercury-containing skin lightening products

Mercury compounds (mercury chloride, ammoniated mercury) were used historically as skin lightening agents and are still found in products manufactured or imported informally in the Caribbean and from West Africa, Southeast Asia, and Latin America.

Mercury is toxic at any dose. Inorganic mercury in skin creams is absorbed through the skin.

Clinical effects of mercury toxicity from skin creams: - Nephrotic syndrome -- the most documented clinical presentation in the literature - Peripheral neuropathy - Tremor, ataxia (organic mercury toxicity pattern, though the predominant form in skin creams is inorganic) - Psychiatric effects (memory impairment, emotional lability) - Fetal harm -- mercury crosses the placenta and the blood-brain barrier. Application by pregnant women represents fetal neurotoxicity risk.

Clinician role: Ask about skin lightening product use in patients presenting with unexplained renal disease, peripheral neuropathy, or neurological symptoms, particularly in women. A 24-hour urine mercury level confirms exposure.

4.4 Corticosteroids in skin lightening products

High-potency corticosteroids -- particularly clobetasol propionate -- are included in some skin lightening products because they cause a degree of skin pallor through vasoconstriction and reduction of melanin synthesis over time. This is not an approved use and produces all the adverse effects described in Section 2: skin atrophy, striae, telangiectasia, steroid rosacea, and adrenal suppression.

Many patients using such products are unaware that they contain a corticosteroid. The adverse skin changes they present with -- skin thinning, stretch marks on the face, visible blood vessels -- are the result of a pharmaceutical they have been using without knowing.

Clinicians should ask about all topical products used on the skin, not only prescribed treatments.

4.5 Tretinoin and retinoids

Tretinoin (retinoic acid) has documented efficacy for post-inflammatory hyperpigmentation, photoaging, and acne. It is available as a prescription product in most Caribbean territories.

It is also found as a component of some skin lightening combinations (hydroquinone + tretinoin + low-potency corticosteroid, the Kligman formula).

Key considerations: - Tretinoin is teratogenic -- Category X in pregnancy (Report 5). Women using any tretinoin-containing product require contraception and must stop immediately on confirmation of pregnancy. - Tretinoin causes initial skin irritation (retinoid dermatitis) -- dryness, peeling, and erythema in the first 2-6 weeks. Patients should be counselled that this is expected and represents drug activity, not an allergic reaction. - Sun protection is essential during tretinoin use -- it increases photosensitivity.

Section 5: Acne -- Getting the Prescribing Right

Acne vulgaris is common across Caribbean populations, affecting approximately 85% of adolescents and a substantial proportion of adults. The prescribing framework:

The antibiotic resistance concern: Prescribing topical clindamycin or erythromycin alone (without benzoyl peroxide) is associated with resistance selection in Cutibacterium acnes. Benzoyl peroxide should always accompany topical antibiotic use, and antibiotic courses should be limited to 3 months with review.

Section 6: The Skin Prescribing Checklist

Section 7: About ElesRx

ElesRx includes drug interaction flagging for systemic antifungals -- ketoconazole, itraconazole, fluconazole -- against the full medication list, identifying CYP450 interactions with warfarin, antidiabetics, statins, and cardiovascular drugs. The system also flags tretinoin and isotretinoin as Category X teratogens when a patient of childbearing age is identified without documented contraception.

The tool is available at elesrx.com. ElesRx is a product of PIPPS Smart Apps, a division of J.C. Epiphany Limited (Jamaica, est. 1998).

Section 8: Methodology and References

8.1 Data sources

Dermatological prescribing data is drawn from the ElesRx clinical database, DailyMed, the British Association of Dermatologists guidelines, and published literature on skin lightening product use in the Caribbean. Mercury toxicity data references published case series and WHO guidance on mercury in skin lightening products.

8.2 Limitations

This report covers common outpatient dermatological prescribing. Specialist conditions (pemphigus, vasculitis, drug reactions, cutaneous lymphoma) and procedural dermatology are beyond its scope.

8.3 Author and conflict of interest disclosure

This report was authored by Juliet Duncan, BPharm, founder of J.C. Epiphany Limited and developer of ElesRx. The author has a commercial interest in ElesRx. This report is published without an access gate as a contribution to Caribbean clinical education. No external funding was received.

8.4 Citation

Duncan J. The Skin Prescribing Report: Topical Corticosteroids, Antifungals, and the Bleaching Problem in Caribbean Practice. ElesRx Clinical Reports, Report 17. Published 2027 at elesrx.com/reports/skin-prescribing-report/. J.C. Epiphany Limited, Jamaica.

References

1. Du Vivier A. Corticosteroids and the skin. Postgrad Med J. 1976;52(608):394-397. doi:10.1136/pgmj.52.608.394

2. Olumide YM, Akinkugbe AO, Altraide D, et al. Complications of chronic use of skin lightening cosmetics. Int J Dermatol. 2008;47(4):344-353. doi:10.1111/j.1365-4632.2008.03558.x

3. WHO. Mercury in skin lightening products. World Health Organization. 2019. who.int/publications/i/item/WHO-CED-PHE-EPE-19-04

4. Ngan V. Tinea incognito. DermNet NZ. Accessed 2027. dermnetnz.org/topics/tinea-incognito

5. Zaenglein AL, Pathy AL, Schlosser BJ, et al. Guidelines of care for the management of acne vulgaris. J Am Acad Dermatol. 2016;74(5):945-973. doi:10.1016/j.jaad.2015.12.037