Solar lentigines and melasma are the two most common causes of acquired facial hyperpigmentation seen in aesthetics practice. Both present as brown discolouration on photodistributed skin, but their aetiology, demographics, dermoscopic features, and treatment pathways are distinct. Getting the differential right before recommending any intervention is not optional. It is the starting point.
What Are Solar Lentigines?
Solar lentigines (the singular is solar lentigo) are flat, well-demarcated macules that form as a direct response to cumulative ultraviolet radiation exposure. They are sometimes called age spots, liver spots, or sun spots, though none of those terms have clinical precision and they are best avoided in documentation.
Clinically, solar lentigines:
- Are uniformly pigmented, typically tan to mid-brown, occasionally darker in fair skin types
- Have sharply defined, sometimes slightly irregular borders
- Appear on chronically sun-exposed sites: face, dorsum of hands, forearms, décolletage, upper back
- Increase in number and size over time with ongoing UV exposure
- Are not influenced by hormonal changes
- Affect men and women roughly equally, predominantly from the fourth decade onwards
Histologically, solar lentigines involve increased melanocyte density in the epidermis and elongated rete ridges. The melanocytes are not structurally abnormal, but they are more numerous per unit area than in surrounding skin, which accounts for the localised pigmentation.
Dermoscopy reveals a characteristic pattern: a diffuse light brown pigmentation with a well-defined fingerprint-like or moth-eaten border. The pattern is epidermal, which is clinically significant because it predicts responsiveness to ablative treatments. A 2025 systematic review in the Journal of Cosmetic Dermatology confirms that solar lentigines respond well to laser, intense pulsed light, chemical peels, and topical retinoids when selected appropriately for skin type.
What Is Melasma?
Melasma is an acquired hypermelanosis driven primarily by hormonal and ultraviolet triggers, with a significant genetic component. It is a condition of melanocyte hyperactivity: the melanocytes are stimulated to produce more melanin, not simply more numerous, which gives it different histological and functional characteristics to solar lentigines.
The clinical presentation:
- Symmetric, bilaterally distributed brown to grey-brown patches
- Three main distribution patterns on the face: centrofacial (forehead, nose, upper lip, cheeks, chin), malar (cheeks and nose), and mandibular (jawline)
- Borders that are irregular and less well-defined than solar lentigines
- Colour variation within a single lesion (epidermal components appear brighter brown, dermal components appear ash-grey)
- Worsens in summer and during hormonal triggers, and may partially fade in winter
Melasma predominantly affects women (approximately 90% of cases), particularly those with Fitzpatrick skin types III to V. Hormonal triggers are the primary driver: combined oral contraceptive pill, pregnancy, hormone replacement therapy, and perimenopause. Sun exposure is the key aggravating factor rather than the sole cause.
A 2026 global expert consensus published in the Journal of the European Academy of Dermatology and Venereology classifies melasma as a photoaggravated hormonal disorder and distinguishes it clearly from solar lentigines in aetiology and in the management framework required.
The Clinical Differences Side by Side
The key differential features practitioners can use at consultation:
| Feature | Solar Lentigines | Melasma |
|---|---|---|
| Aetiology | Cumulative UV damage | Hormonal and UV interaction |
| Sex distribution | Equal (M:F) | Approximately 90% women |
| Age of onset | Fourth decade onwards | Reproductive years |
| Borders | Sharp, well-defined | Irregular, diffuse |
| Colour | Uniform tan to brown | Mixed brown to grey-brown |
| Seasonal variation | Minimal | Marked (worse in summer) |
| Hormonal history | Not relevant | Often OCP, pregnancy, HRT, perimenopause |
| Location pattern | Diffuse photosites | Centrofacial, malar, or mandibular |
| Dermoscopy | Fingerprint or moth-eaten border | Diffuse pseudo-network |
| Wood's lamp | Enhances (epidermal) | Variable (epidermal, dermal, or mixed) |
No single feature makes the diagnosis alone. The clinical picture is built from the full history: age, sex, hormonal history, location pattern, seasonal behaviour, and family history. Melasma has a genetic component that is worth documenting.
Pigment Depth Assessment: Wood's Lamp and Dermoscopy in Practice
Pigment depth assessment changes the treatment plan. The two accessible tools in clinical practice are Wood's lamp examination and dermoscopy.
Wood's lamp emits ultraviolet-A light at 365 nm. Under Wood's lamp:
- Epidermal pigment enhances (appears more intense and well-defined)
- Dermal pigment does not enhance (appears flat or absent)
- Mixed pigment shows inconsistent enhancement across the lesion
Solar lentigines, being predominantly epidermal, enhance under Wood's lamp. Melasma is classified as epidermal, dermal, or mixed. Epidermal melasma enhances. Dermal and mixed types show incomplete or absent enhancement. A lesion that does not enhance under Wood's lamp suggests dermal involvement, which generally predicts a slower, more resistant clinical course.
Wood's lamp is not a replacement for dermoscopy and is not always accurate, particularly in darker skin types where ambient light competes with the lamp. Used in a darkened room after removing skincare, it adds a useful clinical data point rather than a definitive classification.
Dermoscopy gives more granular structural information. The fingerprint-like or moth-eaten border pattern in solar lentigines is epidermal in origin and responds accordingly to treatment. The pseudo-network pattern of melasma reflects a diffuse increase in basal layer pigmentation. Identifying the pattern before recommending a treatment course reduces the risk of post-inflammatory hyperpigmentation from an overly aggressive intervention.
Why the Differential Matters: Treatment Implications
The treatment pathways for solar lentigines and melasma are not interchangeable. Using the wrong approach risks making the presentation worse, not better.
For solar lentigines, the evidence supports:
- Laser treatment: Q-switched Nd:YAG, picosecond lasers, fractional ablative lasers
- Intense pulsed light (IPL): effective for superficial epidermal lentigines on lighter Fitzpatrick types
- Chemical peels: glycolic, lactic, salicylic, and trichloroacetic acid at appropriate concentrations
- Topical maintenance: retinoids plus tyrosinase inhibitors (azelaic acid, kojic acid, niacinamide, arbutin) to slow recurrence
The 2025 systematic review found that laser and light-based treatments produced the highest rates of clearance for solar lentigines, with topical agents used to maintain results and extend the treatment interval.
For melasma, the approach differs in three key ways:
Photoprotection first. Without strict, consistent SPF 50+ use (including visible light and iron-oxide coverage), no topical or in-clinic treatment holds. Recommending topical agents without addressing photoprotection is an incomplete consultation. For clients with melasma, a tinted iron-oxide SPF provides visible-light attenuation that a standard clear chemical SPF does not. Visible light in the blue-violet spectrum also triggers melanogenesis in melasma-prone skin, and this is now recognised in the management standard.
Laser caution. IPL and certain laser modalities that work well for solar lentigines carry a risk of paradoxical darkening or rebound hyperpigmentation in melasma, particularly in Fitzpatrick types IV to VI. The 2026 international consensus recommends laser and light-based interventions only in dermal or resistant melasma, and only after topical preparation, not as a first-line approach. Applying an IPL protocol intended for solar lentigines to a melasma presentation is a documented cause of treatment-resistant cases.
Hormonal context. If the client is on the combined OCP and wants to address melasma, the conversation about contraceptive choice is clinically relevant. Discontinuing oestrogen-containing contraception can reduce the hormonal driver. That decision rests with the client and their prescribing clinician. The practitioner's role is to document the hormonal history, note the potential contribution to the presentation, and ensure it is reflected in the treatment record.
Planning for the Autumn Correction Window
August marks the pre-autumn planning period for UK practitioners. Clients return from summer holidays with increased pigmentation on both fronts: solar lentigines from cumulative UV exposure over the season, and melasma that has worsened under the same sun with hormonal loading.
This is the right moment to:
- Complete thorough pigment assessments before committing to autumn device appointments
- Differentiate the presentations clearly, using history and dermoscopy, before booking any ablative treatment
- Set photoprotection expectations with clients planning in-clinic treatment from September onwards
- Begin topical priming for any client where dermal melasma involvement has been identified, since topical preparation before a procedural intervention reduces the risk of post-inflammatory hyperpigmentation
The assessment process, the clinical differential, the documentation standard, and the treatment decision tree are what Hyperpigmentation Decoded covers in full: the NICE-aligned framework Bernadette's clinic applies throughout the year, including the autumn pigment correction window. If you want a read on where your current knowledge sits before the season opens, the free pigment quiz is the no-commitment starting point.
The Aesthetics Unlocked course catalogue covers the clinical pathway alongside the regulation context. If you are assessing and managing skin conditions as an aesthetic practitioner, both matter.
FAQ
How do I tell solar lentigines from melasma without specialist equipment?
The fastest clinical differentiators are history and pattern. Melasma almost always has a hormonal story: OCP, pregnancy, HRT, or perimenopause. It presents as bilateral, poorly defined patches on the malar area or centrofacial zone. Solar lentigines are scattered, sharply bordered, affect both sexes equally, and have no hormonal history. Those features together are usually enough for a working differential at initial consultation.
Can a client have both solar lentigines and melasma at the same time?
Yes, and they frequently co-exist in perimenopausal women with a history of sun exposure. The assessment needs to map which lesions are which, because treating them as a single presentation produces inconsistent outcomes. Document each area separately and plan accordingly. A treatment that clears solar lentigines on the cheeks may worsen a melasma patch sitting immediately adjacent.
Is Wood's lamp examination reliable for darker skin types?
Wood's lamp is less reliable in Fitzpatrick types V to VI because the contrast is lower and the enhancement effect is harder to read. Dermoscopy tends to give more usable structural information in these skin types. If Wood's lamp assessment is equivocal, default to a conservative topical-first approach rather than a procedural one. The risk of post-inflammatory hyperpigmentation from an aggressive intervention is highest in darker skin types.
Why does melasma recur after treatment but solar lentigines often stay clear?
Solar lentigines recur with renewed UV exposure, but they have no persistent intrinsic driver. Melasma has an underlying hormonal and inflammatory component that can reactivate with UV exposure, hormonal fluctuation, heat, or friction, even after a treatment course has cleared the surface pigment. Maintenance photoprotection and a topical protocol are not optional after melasma treatment. They are part of the plan.
What should I document when assessing a client with facial hyperpigmentation?
As a minimum: age of onset, hormonal history (OCP, pregnancy, HRT, perimenopause), family history of melasma, Fitzpatrick skin type, location and pattern of lesions, whether the presentation worsens seasonally, and any previous treatments tried. Wood's lamp findings and dermoscopy pattern should also be recorded. This documentation supports an accurate differential and provides the baseline against which treatment response is measured.