What causes acne — and what the science says about treating it.

Acne is the most common skin condition worldwide. It is also one of the most frequently mismanaged — because the category "acne" includes several different expressions of the same underlying process, and because the industry has a strong incentive to sell individual products rather than explain the system.

Understanding what causes acne does not require a dermatology degree. It requires knowing four things.

The four-factor model

Acne results from a convergence of four factors, all interacting within the follicle (the pore):

1. Excess sebum production. Sebocytes in the sebaceous gland produce sebum — the skin's natural oil. Androgen hormones (testosterone and its derivatives) regulate sebum production; higher androgen activity increases output. This is why acne becomes common during puberty, worsens at certain points in the menstrual cycle, and is more common in conditions involving androgen excess (such as polycystic ovary syndrome).

2. Abnormal follicular keratinisation. Healthy follicles shed dead skin cells continuously, allowing sebum to flow freely to the surface. In acne-prone skin, this shedding process becomes abnormal — dead cells clump together and accumulate inside the follicle, mixing with sebum to form a plug. This plug (a comedo) is the structural precursor to every type of acne lesion.

3. Cutibacterium acnes (formerly Propionibacterium acnes). C. acnes is a bacteria that colonises the sebaceous follicle. It is present on all skin — it is not the cause of acne by itself. However, in a blocked follicle with elevated sebum, C. acnes proliferates. The bacteria metabolise sebum into fatty acids, and trigger an inflammatory response from the immune system.

4. Inflammation. The immune response to C. acnes — and, increasingly, evidence suggests, to the blocked follicle itself even before bacterial involvement — produces the visible lesions: papules (raised, inflamed bumps), pustules (papules with pus), nodules (deeper, hard lesions), and cysts (deep, fluid-filled lesions). Post-inflammatory hyperpigmentation (the dark marks left after lesions heal) is a consequence of this inflammatory response.

What makes acne worse

Occlusion. Anything that traps sebum in the follicle worsens acne. Heavy, comedogenic moisturisers, certain makeup formulations, and repeated friction (phone screens, chin straps, tight clothing) all increase comedone formation.

Barrier disruption. Stripping the skin with harsh cleansers or over-exfoliating damages the barrier, increases transepidermal water loss, and triggers a compensatory increase in sebum production. Many people with acne over-cleanse, which worsens the sebum load that contributes to it.

Hormonal fluctuation. The androgen-sebum pathway means that acne which is hormonally driven does not respond primarily to topical treatment. Hormonal acne — typically presenting on the jaw, chin, and lower face in adult women — often requires systemic intervention (oral contraceptives, spironolactone) in addition to topicals for meaningful improvement.

Diet (in some people). The evidence for diet and acne is more qualified than popular accounts suggest, but two links are reasonably well established: high-glycaemic index diets increase insulin and insulin-like growth factor 1 (IGF-1), which promotes androgen activity and sebum production; and dairy — particularly skimmed milk — has a documented association with acne in some individuals, possibly through IGF-1 in milk and the effects of certain milk hormones. These are population-level associations; individual responses vary considerably.

The evidence-based treatment hierarchy

Treating acne effectively means addressing at least two of the four factors.

Benzoyl peroxide kills C. acnes directly (the only topical that does so without resistance risk) and has mild keratolytic effects. It is the most reliable over-the-counter topical for inflammatory acne.

Salicylic acid (BHA) is a keratolytic — it penetrates the follicle and dissolves the bonds between dead skin cells, preventing the comedone from forming. Most effective for non-inflammatory (blackhead/whitehead) acne and as a maintenance treatment.

Niacinamide addresses two of the four factors: it has anti-inflammatory effects that reduce redness and lesion severity, and it reduces sebum excretion at concentrations above 2%. It does not kill bacteria or directly clear comedones, but as a supporting ingredient in an acne routine, it reduces the severity of the inflammatory response.

Retinoids are the most effective topical treatment for comedonal acne — they normalise follicular keratinisation directly. Prescription retinoids (tretinoin, adapalene) are significantly more effective than over-the-counter retinol for this purpose. Adapalene is now available over the counter in many markets.

Antibiotics (topical and oral) reduce C. acnes and address the inflammatory component. Due to resistance concerns, they are generally used short-term and in combination with benzoyl peroxide rather than as monotherapy.

Hormonal treatment (combined oral contraceptives, spironolactone) addresses the androgen-sebum pathway in hormonally driven acne. It is often the most effective single intervention for adult women with persistent jaw/chin acne.

The Lux & Glo position

The ritual is not a dedicated acne treatment. It is designed for the population of people who want a sustainable, considered baseline routine — cleansed, treated, and moisturised — that does not aggravate the barrier or worsen inflammation.

The niacinamide serum's anti-inflammatory and sebum-reducing properties make it broadly suitable for acne-prone skin as a supporting active. It does not replace targeted acne treatment where that is clinically indicated. For active, inflammatory acne, the most useful step — before any serum — is the correct diagnosis of whether the acne is hormonal, comedonal, or inflammatory, because the treatment pathway differs for each.

For skin that is post-acne rather than actively congested — dealing with PIH, enlarged pores, uneven texture — the ritual is exactly the right tool.