The subtype-based classification proposed by the NRS 20 years ago [13], although useful, had limitations (Fig. 3). It has since been superseded by a more patient-focused approach, aligning with the latest clinical research and experience (Fig. 3) [1,2,3,4,5].

Evolution of NRS subtype-based classification [13] to current ROSCO phenotype-based classification of rosacea and its variants [1,2,3,4,5]. NRS National Rosacea Society, ROSCO ROSacea COnsensus

This transition to a phenotype approach proposed by the ROSCO expert panel [1,2,3] (Fig. 3), and subsequently by the NRS, recommends rosacea diagnosis and management according to patient presentation of disease features, rather than being constrained by predetermined subtypes. It is recommended that one of the diagnostic features and at least two of the major features are necessary for the diagnosis of rosacea.

A useful table describing common cutaneous features of rosacea forms part of the ROSCO 2019 update [1]. This covers diagnostic features (phymatous changes, persistent erythema aggravated by trigger factors), major features (flushing/transient erythema, papules and pustules, telangiectasia), and minor features (burning, stinging, dryness, edema) [1]. Dermatologists are encouraged to use the most recent guidelines [1,2,3,4,5] to identify the patient’s most problematic symptoms or sequelae (e.g., is it erythema, flushing, papules or pustules, itching, skin-thickening, telangiectasia, ocular rosacea, or other symptoms?).

As rosacea is phenotypically heterogeneous, patients might display several signs and symptoms. Treatments should be tailored to each patient [1,2,3,4,5]. HCPs are advised not to underestimate so-called invisible symptoms of rosacea, such as burning and stinging. Certain therapies available for rosacea can treat beyond the visible rosacea features, targeting underlying inflammation and microbiological causes [14].

More recently, rosacea has been linked to multiple comorbidities, including autoimmune conditions, gastrointestinal disorders, malignancies, cardiovascular disease, depression, migraines, dementia, and Parkinson’s disease [12]. While awareness of these comorbidities is important, it is worth noting that the observed associations are statistical in nature, and the directionality and causality remain uncertain [12]. Guidance on common comorbidities is provided in Fig. 4.

Common comorbidities in rosacea and screening considerations [12, 15]. Figure abridged from Haber and El Gemayel, 2018 [12]. BMI body mass index, CVD cardiovascular disease, HbA1c glycated hemoglobin

The developing concept of the gut–skin axis, and its involvement in the pathogenesis of many chronic inflammatory diseases, asserts that gastrointestinal health affects the skin homeostasis and allostasis through multifaceted interactions between the immune, metabolic, and nervous systems [15]. As a major regulator of this axis, the gut microbiome is strongly implicated, specifically regarding bidirectional modulation between the gut microbiome and host immunity [15].

Genetic and environmental factors can exacerbate or trigger rosacea partly through the release of neuropeptides, which can lead to the development of rosacea lesions [10]. The REACH GSC advises that trigger avoidance should be approached with sensitivity, recognizing that for some patients, the burden of restrictions can outweigh the burden of the disease itself; however, avoiding triggers during disease flares or exacerbations is still recommended. That said, when patient improvement is seen, it is worth examining whether it coincides with triggers being avoided, minimized, or removed. The REACH GSC highlighted certain treatments may act as triggers for some patients and overuse of steroids, when self-managing rosacea, can present problems.

Discerning how rosacea features might affect a patient’s quality of life (QoL) remains an important line of inquiry, and the better understanding an HCP has of their patient’s disease state, the better the opportunity for individualized treatment plans, maintenance, and successful outcomes. Evidence has shown that patients with rosacea have an increased risk of developing depression and anxiety, and certain rosacea features, especially erythema and flushing, may be particularly debilitating [16]. Effective treatment of clinical features brings significant improvement in psychological features; nonetheless, psychological support should be made available if thought beneficial for the patient [16]. The need to cleanse, treat, moisturize, and protect (CTMP) has been emphasized in the literature, where patients achieved greater success with combination treatments when actively using cleansers, moisturizers, and sunscreen alongside their treatment [4].

Rosacea is often characterized by dry, easily irritated, sometimes sensitive skin, where a disrupted skin barrier has increased trans-epidermal water loss and facilitated penetration of potential irritants or allergens [17]. Dermatologists should be aware that sensitive skin syndrome is not an immunological disorder but is related to alterations of the dermal nervous system (e.g., involvement of unmyelinated C-fibers and of transient receptor potential of the vanilloid subtype [TRPV] channels), and in certain subgroups, psychosocial factors (e.g., stress) might be relevant [18, 19]. The Sensitive Scale-10 is a tool to better define and assess sensitive skin syndrome and allows a comprehensive evaluation of dermocosmetic skincare products over time on key parameters relating to skin sensitivity [19, 20]. A total of 2966 patients presenting with sensitive skin were included in a study from 11 countries to validate the Sensitive Scale-10 diagnostic tool worldwide in patients presenting with sensitive skin, including patients with rosacea (9%) [20]. The study concluded the Sensitive Scale-10 was the first to measure the severity of skin sensitivity and then enable the measurement of variations pre- and post-treatment [20].

Rosacea is under-recognized, underdiagnosed, and more difficult to discern in skin of color. For patients with Fitzpatrick skin types IV–VI, rosacea may well manifest/appear differently, with erythema being difficult to detect [21] (Fig. 5). In these cases, a full medical history considering family history and any prior history of acne diagnosis, as well as following the ROSCO/AARS/NRS diagnostic criteria, are advised to aid in deciding the most appropriate treatment selection [1,2,3,4,5].

Case study examples of rosacea in skin of color, skin phototype IV. A 28-year-old male of skin phototype IV complained of persistent facial erythema with papules and pustules. Patient reported facial erythema since childhood with seborrheic dermatitis and recent failed acne treatments. (i) In June 2023, he was commenced on isotretinoin 10 mg once daily, azithromycin 500 mg 3×/week for 6 weeks, and azelaic acid cream 15% before bedtime. Desonide cream 0.05% prescribed as needed for flares of seborrheic dermatitis along with regular use of mild cleanser, hydrating moisturizer, and silicone-based sunscreen. (ii) In October 2023, erythema, facial edema, and papules and pustules improved dramatically and isotretinoin 10 mg was reduced to 2 ×/week for a further 2 months. Azelaic acid cream 15% was maintained before bedtime. Daily sunscreen, mild cleanser, and hydrating moisturizer continued throughout. Images taken using 3DLifeViz mini by QuantifiCare (Biot, France). Images courtesy of Dr Johannes Dayrit with patient’s consent

Ocular manifestations of rosacea, such as lid margin telangiectasia, blepharitis, keratitis, conjunctivitis, and anterior uveitis are commonly overlooked. As eye health and vision might be affected, ophthalmological referral should be sought for all but mild forms of ocular rosacea [1, 2]. The ROSCO recommendations provide helpful information for dermatologists in deciding the severity of ocular symptoms [1].

Phymatous rosacea should be assessed according to both its stage of development (early or fibrotic), the level of facial edema, and the extent of inflammation (active or burnt out), as treatment will differ accordingly [1, 4]. Features include erythema, thickening of the skin, irregular surface nodularities, and enlargement of the pilosebaceous poral orifices (in rhinophyma) (Fig. 6). It is worth examining beyond the nasal region as it may occur on the cheek, nose (rhinophyma), chin (gnatophyma), forehead (metophyma), periorbital region (blepharophyma), or ear (otophyma) [22]. It is relevant to mention Morbihan’s disease here—a rare condition and complication of rosacea—that is characterized by chronic and persistent erythematous solid edema localized on the face, which is frequently treatment-refractory [23].

Case study example of mild rhinophyma. A 59-year-old male with a 15-year history of rosacea with mild rhinophyma. Previous doxycycline treatment (50–100 mg/day, 6–8-month treatment periods) for the past 10 years had initially controlled inflammatory symptoms (erythema, papules, and pustules) but had become increasingly ineffective. His doxycycline was ceased and he was switched to isotretinoin, 20 mg/day, for 4 weeks, reducing to 10 mg/day. He was commenced on a skincare regimen, including a cream-based cleanser at night followed by a simple hydrating moisturizer, with a high sun protection factor broad-spectrum sunscreen every morning. The images above show results at (i) 12 months maintaining skincare and 10 mg isotretinoin; and (ii) 18 months with continued isotretinoin and pulsed dye laser over the nose cheeks and chin, showing excellent control of papules and pustules, and dramatic shrinking of nasal swelling. Images courtesy of Dr Belinda Welsh with patient’s consent

Granulomatous rosacea is a clinically distinct form of rosacea where patients present with firm brown, yellow, red, or flesh-colored papules or nodules on the cheeks or around the eyes, nose or mouth on relatively healthy-looking skin [24, 25]. Histological differentiation may be needed, typified by noncaseating granulomas, which are seen in the superficial and mid dermis [24] (Fig. 7).

Case study of granulomatous rosacea. A 38-year-old female with a 7-year history of diffuse facial erythema, flushing, sensitivity, with periods of exacerbations and remissions, but no previous medical treatment. Initially appearing after the birth of her first child and worsening 3 years later after the birth of her second child. Condition possibly triggered or aggravated after using a home microdermabrasion machine. Clinically diffuse and perifollicular erythema papules and follicular micropustules extending to the lateral cheeks with associated mild melasma. The lateral follicular micropustules suggest possible coexistent pityrosporum folliculitis. Biopsy revealed upper dermal telangiectasia and perivascular lymphoplasmacytic inflammation with small perivascular and appendageal granulomas. Commenced on doxycycline 100 mg but ceased after 2 weeks due to indigestion and headaches, moved to ivermectin 1% cream. Commenced on isotretinoin 10 mg per day for 4 months, then 10 mg 3 × per week for a further 8 months. Daily sunscreen, night cleanser, and moisturizer as skincare throughout. Excellent clinical response but took many months to clear. Images courtesy of Dr Belinda Welsh with patient’s consent

Scalp involvement of rosacea is a rare diagnosis, seldom reported in literature. It poses a diagnostic challenge owing to its atypical presentation and the possibility of being associated solely with mild facial lesions. Primarily affecting males, clinical presentation includes erythema and sometimes papules and pustules and peripilar scaling (resembling that found in lichen planopilaris) [26, 27].

Rarer variants of rosacea have been recorded, such as neurogenic rosacea that has prominent neurological symptoms, including severe flushing and burning, stinging, and dysthesias, and does not respond well to conventional therapy [28, 29].

It has been well documented that, in genetically susceptible individuals, Demodex mites play a central involvement in rosacea pathophysiology [30,31,32,33]. From a diagnosis and treatment perspective, in some patients with rosacea, eradication of Demodex appears to alleviate rosacea features—it is assumed by preventing the formation of proinflammatory cytokines [31].

Histological results can provide further insights into the disease state of the patient, which can depend on the rosacea subtype under study (e.g., papulopustular or erythematotelangiectatic area) [14, 33, 34]. Although histopathological findings are broadly similar across rosacea phenotypes, subtle variations may be observed depending on inflammatory intensity and the presence of Demodex-associated changes [14, 34]. Owing to its invasive nature, biopsy is seldom required.