Anti-Wrinkle Injections: What the Different Products Are, How Dosing Works, and Why Resistance Is Real
If you've ever wondered why your practitioner uses a particular product, or why your dose changed between appointments, or why someone you know stopped responding to treatment after years of good results, this is the post for you.
Anti-wrinkle injections are one of the most commonly performed cosmetic treatments in New Zealand. But the conversation around them is often surprisingly shallow. Most content stops at "it relaxes the muscle" and moves straight to aftercare. What gets left out is the part that actually matters: that different products behave differently, that dosing is a clinical decision with real variables behind it, and that resistance is a genuine phenomenon with a biological explanation.
I want to change that. Not to overwhelm you with information, but because I think patients who understand what's happening get better outcomes. They ask better questions, they have more realistic expectations, and they're better placed to notice when something isn't right.
So let's start at the beginning.
The Terminology, Sorted
You'll hear several terms used interchangeably, and it creates unnecessary confusion. Here's what they actually mean.
Botulinum toxin type A is the active ingredient in all anti-wrinkle injectable products. It's a purified protein that temporarily blocks the nerve signal to a muscle, preventing it from contracting with full force. The wrinkle softens because the muscle causing it is no longer working as hard.
Neuromodulator is the clinical term for this class of treatment. It's accurate and non-brand-specific, which is why practitioners often use it.
Anti-wrinkle injection is the plain-English version. It describes what the treatment does without naming a specific product.
Botox is a brand name, not a generic term. Calling all anti-wrinkle injections "Botox" is like calling all vacuum cleaners a Hoover. It's become common shorthand, but it refers to one specific product made by Allergan Aesthetics.
All four terms describe the same category of treatment. The differences lie in the specific products within that category, and that's where it gets interesting.
The Products Available in New Zealand
There are currently four botulinum toxin type A products approved by Medsafe for use in New Zealand: Botox, Dysport, Xeomin, and Relfydess. They all work through the same mechanism, but they are not identical, and the differences matter clinically.
The core distinction comes down to two things: molecular structure and the presence or absence of complexing proteins.
Botulinum toxin type A exists as a core neurotoxin molecule. In some products, that core molecule is surrounded by accessory proteins, sometimes called complexing proteins. In others, it isn't. This affects how the product behaves in tissue, how quickly it spreads, and, critically, how the immune system responds to it over time.
Here's how the four products compare:
Botox (onabotulinumtoxinA) is the most established product globally and has the largest body of clinical evidence behind it. It contains complexing proteins. Onset is typically three to five days, with full effect at around two weeks. Duration is generally three to four months, though this varies by individual and area treated.
Dysport (abobotulinumtoxinA) also contains complexing proteins and has a slightly different unit formulation to Botox, meaning doses are not directly interchangeable on a one-to-one basis. It tends to have a faster onset, often two to three days, and spreads slightly more in tissue. This can be an advantage in larger muscle groups like the forehead, and a consideration in areas where precision is critical.
Xeomin (incobotulinumtoxinA) is what's known as a "naked" toxin. The complexing proteins have been removed, leaving only the pure active molecule. This has implications for immunogenicity, which I'll come back to in the resistance section. Onset and duration are broadly similar to Botox, though some patients report a slightly different quality of result.
Relfydess (prabotulinumtoxinA-xvfs) is the newest product available in New Zealand. It is also protein-free, like Xeomin, and is formulated to be stored at room temperature, which is a practical difference from the other three. Clinical data supports comparable efficacy and duration to established products, and its protein-free formulation makes it a clinically interesting option for patients with a history of reduced treatment response.
No single product is universally superior. Each has a profile that makes it more or less suited to a given patient, a given area, and a given treatment goal. Choosing between them is a clinical decision, not a preference for a brand.
How Dosing Decisions Are Made
This is the question I get most often in consultations, usually phrased as: "How do you know how much to use?"
The honest answer is that dosing is not a formula. It's a clinical judgement informed by several variables assessed at the time of treatment. Here's what I'm actually considering.
Muscle mass and strength. Muscles vary significantly between individuals. A patient with a strong, well-developed masseter muscle requires a meaningfully different dose than someone with a naturally softer jaw. The same applies to the frontalis, the corrugator, and every other muscle we treat. Underdosing a strong muscle produces a weak, short-lived result. Overdosing a weaker muscle can produce an over-treated look that nobody wants.
Sex and hormonal factors. On average, men have greater muscle mass and require higher doses to achieve comparable results. This isn't a universal rule, but it's a reliable starting point. Hormonal changes, including those associated with menopause, can also affect how the skin and underlying muscle respond to treatment over time.
The area being treated. Different areas of the face call for different approaches. The forehead, for example, is a balance: too little and the result is negligible, too much and the brow drops. The crow's feet area requires precision around the orbicularis oculi to soften lines without affecting natural eye movement. The glabella, the area between the brows, often tolerates a more robust dose because the muscles there are typically strong and the aesthetic goal is usually significant relaxation.
The desired effect. Some patients want a very natural result, subtle softening with full expression preserved. Others want more significant relaxation. Both are valid, and both require different doses. Understanding what a patient is actually after is as important as any physical assessment.
Treatment history. A patient who has been treated regularly for several years may have some degree of muscle atrophy from repeated relaxation, meaning they need less product over time. Conversely, a patient who has had inconsistent treatment or long gaps may need a recalibration.
I always start conservatively with new patients and review at two weeks. It's straightforward to add at a review. It's not straightforward to undo a result that went further than intended. That two-week appointment isn't a formality. It's part of the treatment.
Resistance: What It Is and Why It Happens
Resistance to botulinum toxin is one of the most misunderstood topics in aesthetic medicine, and it deserves a straightforward explanation.
True immunological resistance occurs when the body develops neutralising antibodies against the botulinum toxin molecule. These antibodies bind to the toxin and prevent it from working. The result is that treatment becomes less effective over time, or stops working altogether. This is not a myth, and it is not rare enough to dismiss.
The clinical evidence is clear on what drives antibody formation. Research published in the journal Toxins and reviewed across multiple NIH PubMed studies identifies two primary risk factors: high doses and frequent treatments. The more toxin protein the immune system is exposed to, and the more often it's exposed, the higher the likelihood of an antibody response developing.
This is where the complexing proteins become clinically relevant. Products that contain accessory proteins expose the immune system to a larger total protein load with each treatment. The core neurotoxin is the active component, but the surrounding proteins are also foreign to the body and can trigger an immune response. Products like Xeomin and Relfydess, which contain only the purified active molecule, present a lower total protein load. The theoretical advantage is a reduced immunogenic stimulus over time.
This doesn't mean protein-containing products are unsafe or that everyone who uses them will develop resistance. Most people don't. But for patients who are treated frequently, at higher doses, or who have already noticed a reduction in how long their results last, protein load is a relevant clinical consideration.
There's also what's sometimes called functional resistance, which is different. This describes a situation where treatment response diminishes not because of antibodies, but because of factors like product dilution, incorrect placement, or muscle adaptation. It can look like true resistance but has different causes and different solutions.
Why does this matter for how I practice? Because conservative dosing isn't just about getting a natural result on the day. It's about protecting the long-term effectiveness of treatment. A patient who develops true resistance has very limited options. Switching to a protein-free product may help in early stages, but once neutralising antibodies are well established, the treatment window can close. That's a significant outcome to try to prevent.
My approach has always been to use the lowest effective dose and to space treatments appropriately. It's not the fastest path to a result, but it's the most sustainable one.
What This Means for Your Treatment
If you're considering anti-wrinkle injections for the first time, or you're an existing patient wondering why your practitioner makes the choices they do, I hope this gives you a clearer picture.
The product matters. The dose matters. The frequency matters. And none of those decisions should be made without a proper assessment of your individual anatomy, your treatment history, and your goals.
At Bezar, every appointment includes time to reassess. I'm not just injecting to the same map each visit. I'm looking at how your face has changed, how the previous treatment performed, and whether any adjustments are warranted. That's what a treatment plan actually is, as opposed to a repeated procedure.
If you have questions about which product I use for you and why, please ask. I'm happy to explain the reasoning. That conversation is part of what I think good care looks like.
Mandatory Product Statements
In accordance with New Zealand therapeutic advertising requirements, the following mandatory statements apply to the products named in this article.
BOTOX (onabotulinumtoxinA) is a prescription medicine for the treatment of frown lines, forehead lines, and crow's feet. It contains botulinum toxin type A 100 units. Ask your doctor if BOTOX is right for you. BOTOX has risks and benefits. Cautions: do not use if you have an infection at the injection site, are pregnant or breastfeeding, or are allergic to any ingredient. Tell your doctor about all medicines and supplements you are taking. Side effects: temporary bruising, headache, and local pain. If you have side effects, see your doctor, pharmacist, or healthcare professional. You need a prescription for BOTOX. Allergan Aesthetics, an AbbVie company.
DYSPORT (abobotulinumtoxinA) is a prescription medicine for the treatment of frown lines. It contains botulinum toxin type A 500 units. Ask your doctor if DYSPORT is right for you. DYSPORT has risks and benefits. Cautions: do not use if you have an infection at the injection site, are pregnant or breastfeeding, or are allergic to any ingredient. Tell your doctor about all medicines and supplements you are taking. Side effects: temporary bruising, headache, and local pain. If you have side effects, see your doctor, pharmacist, or healthcare professional. You need a prescription for DYSPORT. Ipsen.
XEOMIN (incobotulinumtoxinA) is a prescription medicine for the treatment of frown lines. It contains botulinum toxin type A 100 units. Ask your doctor if XEOMIN is right for you. XEOMIN has risks and benefits. Cautions: do not use if you have an infection at the injection site, are pregnant or breastfeeding, or are allergic to any ingredient. Tell your doctor about all medicines and supplements you are taking. Side effects: temporary bruising, headache, and local pain. If you have side effects, see your doctor, pharmacist, or healthcare professional. You need a prescription for XEOMIN. Merz Aesthetics.
RELFYDESS (prabotulinumtoxinA-xvfs) is a prescription medicine for the treatment of moderate to severe frown lines. It contains botulinum toxin type A 50 units. Ask your doctor if RELFYDESS is right for you. RELFYDESS has risks and benefits. Cautions: do not use if you have an infection at the injection site, are pregnant or breastfeeding, or are allergic to any ingredient. Tell your doctor about all medicines and supplements you are taking. Side effects: temporary bruising, headache, and local pain. If you have side effects, see your doctor, pharmacist, or healthcare professional. You need a prescription for RELFYDESS. Evolus.
