Reference

The skin dictionary.

46 terms you will meet in a skin clinic, on a product label, or in something you read at midnight — defined plainly, each with one honest limit. It is a reference, not a recommendation: it says what things are, never what you should use.

Registered nurse–led · Springvale, Victoria · Updated August 2026

On this page

Ingredients

What actually goes on skin, and what each thing does.

Treatments

The procedures and the words attached to them.

How skin behaves

The words for what skin does, as distinct from what is wrong with it.

The industry

Terms about how this business works — including the ones it would rather you did not ask about.

Ingredients

What actually goes on skin, and what each thing does.

Each entry states what the thing is, then one thing it does not do. The second half is usually the more useful one.

Retinoid: The family name for vitamin A derivatives used on skin — retinol, retinal, retinyl esters and prescription retinoic acid. They increase the rate at which skin cells turn over. Strength runs in that order, with prescription forms strongest.; The limit: Almost all of them cause a period of dryness and flaking when first introduced. That is expected, is not an allergic reaction, and is not by itself a reason to stop — but it is a reason to have had someone tell you it was coming.
Retinol: The most common over-the-counter retinoid. Skin converts it in two steps before it becomes active, which makes it gentler and slower than the forms further along that chain.; The limit: Percentage on a label is a poor guide to strength. Formulation, packaging and how stable the product is matter as much, and a high number in a jar exposed to light can do less than a low one in an airless pump.
Retinal (retinaldehyde): One conversion step closer to the active form than retinol, so it works faster at a comparable concentration. Sometimes spelled retinaldehyde. Not the same word as retinol, despite the single letter.; The limit: Faster also means less forgiving on reactive skin. The step up from retinol is not automatically an upgrade for everyone.
Vitamin C (ascorbic acid): An antioxidant used in the morning. L-ascorbic acid is the most studied form; the various ascorbyl derivatives are more stable and generally less potent.; The limit: It oxidises with light and air. A serum that has turned orange or brown has already degraded, and small opaque packaging is a feature rather than a way of selling you less.
Niacinamide: Vitamin B3. Supports barrier function and is one of the few actives most skin tolerates without a settling-in period.; The limit: The high percentages that get marketed hardest are not obviously better than moderate ones, and above a certain concentration some people find it causes flushing.
AHA (alpha hydroxy acid): Water-soluble acids — glycolic, lactic, mandelic — that loosen the bonds holding dead cells at the surface. Glycolic has the smallest molecule and penetrates most; mandelic the largest and least.; The limit: They increase sun sensitivity, which is the part most often skipped. Using an AHA without daily sunscreen works against itself.
BHA (beta hydroxy acid): Salicylic acid, almost always. Oil-soluble, which means it can get into a pore where a water-soluble acid cannot. That single difference is the whole reason to choose one over the other.; The limit: Being able to reach further into a pore is not the same as being gentler. It is still an acid and still exfoliating.
Benzoyl peroxide: An antibacterial agent used on inflammatory breakouts. Available over the counter in a range of strengths.; The limit: It bleaches fabric — towels, pillowcases, collars — and it degrades some other actives it is layered with. Neither fact appears on most packaging.
Hyaluronic acid: A humectant: it binds water and holds it in the upper layers of skin. Occurs naturally in the body; the version in skincare is manufactured.; The limit: It draws moisture from wherever it can find it. In a dry environment, applied to dry skin with nothing sealing it in, it can pull water out of the skin rather than into it.
Ceramide: One of the lipids that make up the skin's own barrier, alongside cholesterol and fatty acids. Topical ceramides supplement what is already there.; The limit: They support recovery rather than driving change. Skin that has been over-treated often needs this category and no more for a while, which is an unexciting answer people resist.
Squalane: A stable, lightweight emollient. The saturated form of squalene, which the skin produces naturally; the version in products is usually plant-derived.; The limit: It softens and seals but does not hydrate on its own — there is no water in it. It works with a humectant rather than instead of one.
Peptide: Short chains of amino acids used as signalling ingredients rather than exfoliants. Gentler than acids and retinoids, and slower to show anything.; The limit: The category with the widest gap between marketing language and published evidence. Some are well studied; many are named to sound as though they are.
Azelaic acid: A dicarboxylic acid used on congestion and uneven tone. Available over the counter at low strengths and by prescription higher.; The limit: It can sting on application for the first week or two even where it is well tolerated afterwards.
SPF: Sun protection factor: a measure of protection against UVB, the wavelength primarily responsible for burning. In Australia, sunscreens are regulated as therapeutic goods by the TGA.; The limit: SPF says nothing about UVA, which is what 'broad spectrum' covers separately. And the rated number assumes an application thickness most people never use.
INCI: International Nomenclature of Cosmetic Ingredients — the standardised naming system on every ingredient list, ordered by concentration down to 1%.; The limit: Below 1% the order means nothing, and that is where most of the actives a product is marketed on tend to sit.
Comedogenic: Describes an ingredient held to be more likely to contribute to blocked pores. The ratings in circulation come largely from mid-century animal-ear testing.; The limit: The scale is widely quoted and poorly evidenced for human faces in finished formulations. An ingredient's rating in isolation says little about the product it sits in.
Fragrance / parfum: A single INCI term covering any number of undisclosed aromatic compounds. Includes ingredients added to mask a base smell, which is why 'unscented' and 'fragrance-free' are not the same claim.; The limit: It is one of the more common causes of contact reaction, and because the term is a container rather than a compound, a reaction cannot be traced to a specific thing.

Treatments

The procedures and the words attached to them.

Each entry states what the thing is, then one thing it does not do. The second half is usually the more useful one.

Dermaplaning: Manual exfoliation with a sterile surgical blade drawn flat across taut skin, removing the outer layer of dead cells and the fine vellus hair with it.; The limit: It does not change pigment or anything below the surface. And the hair does not grow back thicker — the follicle is unchanged; only the cut end feels different.
Microdermabrasion: Physical exfoliation by instrument: an abrasive tip passed over the skin under vacuum, lifting the outer layer as it goes.; The limit: Surface only, and it suits skin that is not already reactive. Regularity matters more than intensity in any single session.
Chemical peel: A controlled application of acid that dissolves the bonds between surface cells so they shed. Depth is set by the acid, its concentration, its pH and how long it stays on.; The limit: 'Peel' covers everything from a lunchtime refresh to a medical procedure with real downtime. The word alone tells you almost nothing about what you are booking.
Microneedling: Fine needles create controlled micro-injuries in the skin to prompt a repair response. Depth is set to the area and the intention.; The limit: It works over a series and not in one session, and it is not appropriate on skin that is actively inflamed or broken.
BioRePeel: A branded biphasic solution applied to the skin, often in the same appointment as needling. At Glow the two are one combined treatment rather than separate bookings.; The limit: Because it is a proprietary formulation, comparisons with generic peels are approximate at best.
Hydradermabrasion: Exfoliation combined with simultaneous infusion of fluid, rather than dry abrasion. The category several trademarked devices belong to.; The limit: Device brands in this space are marketed as though they were distinct treatments. The underlying mechanism is largely shared.
LED therapy: Exposure to specific wavelengths of light, most often red or blue, usually added to another treatment rather than booked alone.; The limit: Dose and duration vary enormously between devices, and evidence is stronger for some wavelengths and intentions than others.
PRP: Platelet-rich plasma: a person's own blood, separated so the platelet-rich portion can be reapplied. Involves a blood draw.; The limit: Glow does not currently offer this. It is withdrawn while a regulatory question about how it should be provided in a nurse-led clinic is answered.
Exosomes: Extracellular vesicles used in topical preparations, generally applied after a treatment that has opened a channel into the skin.; The limit: The regulatory position depends heavily on how a preparation is used — topical application and injection are different questions. Glow offers the topical route only.

How skin behaves

The words for what skin does, as distinct from what is wrong with it.

Each entry states what the thing is, then one thing it does not do. The second half is usually the more useful one.

Skin barrier: The outermost layer of skin together with the lipids between its cells — the part that holds water in and keeps irritants out.; The limit: Almost everything marketed as an active works against the barrier in the short term. A plan that ignores recovery time is a plan that produces reactive skin.
TEWL: Transepidermal water loss: the water that evaporates through the skin continuously. It rises when the barrier is compromised.; The limit: It is a measurement, not a diagnosis. Raised TEWL says the barrier is not holding water well; it does not say why.
Dry vs dehydrated: Dry skin lacks oil and is a skin type. Dehydrated skin lacks water and is a condition — temporary, and it can happen to oily skin.; The limit: Confusing the two is one of the most common reasons a routine fails: oil added to skin that needed water changes nothing that was bothering you.
Purging vs breaking out: Purging is a temporary increase in visible congestion when something speeds up cell turnover, bringing existing blockages to the surface sooner. Breaking out is a reaction to a product that does not suit.; The limit: The genuine distinction is where and how long. Purging appears where you usually congest and settles within a few weeks; a reaction appears in new places and does not. Nobody can tell you which yours is from a description alone.
Vellus hair: The fine, soft, usually pale hair covering most of the face and body. Distinct from terminal hair, which is thicker and pigmented.; The limit: Removing it does not convert it to terminal hair. Follicle type determines that and cutting does not change a follicle.
Telangiectasia: Small blood vessels near the skin's surface that have dilated enough to be visible. The everyday name is 'broken capillaries', which is a misnomer — nothing is broken.; The limit: Skincare can reduce how reactive the surrounding skin is. It does not close a vessel; that generally requires vascular laser or IPL, which Glow does not offer.
Post-inflammatory hyperpigmentation: The flat brown or grey mark left behind after inflammation has resolved — a spot, a scratch, a reaction. It is pigment, not scarring.; The limit: It usually fades on its own over months, and sun exposure is what makes it last. It is frequently mistaken for scarring, which is a different thing needing a different answer.
Photoageing: Changes attributed to cumulative UV exposure rather than to time passing — pigment, texture and loss of elasticity.; The limit: Distinguishing it from chronological change matters because they respond differently, and only one of them can still be influenced going forward.
Skin type: A description of how skin behaves at baseline — how much oil it produces, how easily it reacts, how well it holds water.; The limit: It is not fixed for life, and it shifts with season, age, medication and what has been put on it. A type assigned once and never revisited is often the reason a routine stopped working.
Patch test: Applying a small amount of a new product to a limited area for several days before using it on the face.; The limit: It catches obvious reactions. It does not catch delayed sensitivity or cumulative irritation from a combination of products, which is a more common way things go wrong.

The industry

Terms about how this business works — including the ones it would rather you did not ask about.

The terms that describe how clinics operate. Several of them are the reason this site looks different to others you have read.

Registered nurse (RN): A nurse registered with AHPRA under Australia's national registration scheme, with a defined scope of practice and continuing obligations.; The limit: Registration is verifiable and public — anyone can look up a practitioner on the AHPRA register. 'Skin therapist' and 'aesthetician' are not protected titles in Australia and require no registration at all.
Scope of practice: The range of activity a practitioner is educated, competent and authorised to perform. It differs by registration, not by confidence.; The limit: It is why an assessment can end in a referral. Being told something is outside a clinic's scope is the system working, not the appointment failing.
AHPRA: The Australian Health Practitioner Regulation Agency — the body that registers health practitioners and administers the national law, including the advertising rules.; The limit: Its cosmetic procedure guidelines, in force since September 2025, are why clinics stopped publishing testimonials and before-and-after images for certain treatments.
TGA: The Therapeutic Goods Administration — Australia's regulator for medicines, medical devices and biologicals, including how they may be advertised.; The limit: It is why no clinic in Australia may advertise prescription-only injectables to the public, and why this site names none. The rule binds the advertiser, not the practitioner.
ARTG: The Australian Register of Therapeutic Goods. A product must generally be included on it to be lawfully supplied as a therapeutic good.; The limit: 'Cosmetic' on a label is not the same as ARTG inclusion, and a cosmetic that makes a therapeutic claim is being represented as a therapeutic good regardless of what the label says.
Prescription-only medicine: A medicine that may only be supplied on the prescription of an authorised prescriber, after an individual consultation.; The limit: It cannot be advertised to the public in Australia, directly or indirectly. That includes describing the treatment without naming the product.
Informed consent: Agreement to a procedure given after being told what it involves, what it will not do, what can go wrong, and what the alternatives are — including doing nothing.; The limit: Signing a form is the record of consent, not the consent itself. If nobody talked you through the alternatives, the conversation did not happen.
"Prices on enquiry": A published position that a price will be given only after contact is made.; The limit: A price you have to ring for is a price that can change depending on who is asking. Every price at Glow is published on one page, and it is the same for everyone.
Skin plan: A written document produced at consultation: assessment findings, staged recommendations, the order things run in, the timing between them, and a home regime.; The limit: It is yours and it is portable — you can take it to another clinic. A plan that only exists in a clinic's own system is a record of their decisions, not yours.
Consultation fee: A charge for assessment time, distinct from a treatment charge.; The limit: Where the fee is credited against treatment, the assessment is functionally a sales appointment with a deposit attached. Glow's $150 is not credited, which is what keeps 'do nothing yet' an available answer.

What this is

Definitions are not a plan.

Knowing what niacinamide is will not tell you whether you should be using it, at what strength, or alongside what else. Every entry here is deliberately a definition and a limit — not a recommendation.

We will not assemble these into a routine for you, and that is on purpose. Plenty of sites will. What they cannot do is look at your skin, and the answer changes completely once someone has.

What this is good for: understanding what you already own, working out why something stopped working, and asking a better question when you do sit down with a nurse.

Ingredients, in more depth

The eight actives that actually change skin, and what each will not do.

What your skin is doing

Nine patterns people arrive with, described rather than diagnosed.

What a consultation covers

Ninety minutes, $150, and you leave holding a written plan.