Forehead Wrinkles: What Causes Them and Which Treatment Fits Your Type

Forehead wrinkles don't have a single cause. The horizontal lines that appear when you raise your eyebrows usually come from the frontalis muscle folding the skin again and again. Lines that stay visible when your face is relaxed involve accumulated movement, falling collagen, sun exposure, dryness and changes in the tissue under the skin. Some people also use their forehead to hold their brows up all day, because the brows sit low or the upper eyelids are heavy. Relax that muscle with an injection without checking for this, and you can end up with heavy-feeling eyes or a dropped brow.

So the answer to “how do I get rid of forehead wrinkles?” shouldn't start with a number of units or the name of a machine. It should start with whether the lines show only when you move or also at rest, what your brows and eyelids are doing, how much sun damage your skin has, and what kind of expression you want to keep.

This article helps you tell the line types apart and compares options from sunscreen and retinoids to botulinum toxin, lasers, lifting devices, filler and surgery, with an honest account of contraindications, risks and the results you can expect.

Quick summary before you read

• Lines that show only when you raise your brows are called dynamic lines, and they're natural movement.
• Lines visible even when your face is still are static lines. They usually involve both muscle force and skin quality, so they may need treatment on several levels.
• Botulinum toxin suits muscle-driven lines, but the brows, eyelids and the frontalis's compensating role must be assessed first to lower the risk of heavy eyes or a dropped brow.
• Skincare and lasers help skin quality and shallow lines, but can't stop the muscle from moving the way botulinum toxin does.
• Filler in the forehead carries a risk to blood vessels and vision. It isn't the first choice for everyone, and approved uses vary by product and country.
• No method makes lines disappear permanently. A reasonable goal is softer lines, a more relaxed look and the ability to still show emotion.
• If facial droop, a drooping eyelid or muscle weakness appears suddenly along with weakness in an arm or leg or slurred speech, call 1669 (Thailand's emergency medical line). Don't assume it's only wrinkles.

What types of forehead wrinkles are there?

Dynamic lines: lines you see when you make an expression

When you raise your brows, the frontalis muscle lifts them and folds the forehead skin into horizontal lines. These can appear in your twenties and aren't always a sign of damaged skin. When the muscle relaxes, the lines soften or disappear.

Dynamic lines respond well to botulinum toxin, because the drug temporarily reduces the nerve signal to the muscle, so there's less force folding the skin. But injecting too much, or in the wrong place, can weaken the brow lift you need to keep your eyes open comfortably.

Static lines: lines you still see when your face is still

After the skin has been folded repeatedly for a long time, and collagen and elasticity have fallen, lines can stay even while the muscle rests. These often improve partly when muscle force is controlled, but botulinum toxin alone won't necessarily erase them. They may need added skincare, resurfacing laser or other methods, depending on depth and skin tone.

Fine lines from dry skin or photoaging

Dehydrated skin makes fine lines look sharper, while UV radiation gradually degrades collagen and skin structure. These lines tend to be fine and widespread, often with rough texture, sun spots or uneven color. Caring for the skin barrier and protecting against sun matter more than injecting every line.

Frown lines between the brows aren't horizontal forehead lines

The vertical lines between the brows come from the corrugator and procerus muscles, which pull the brows down and together. The horizontal lines come from the frontalis, which lifts the brows. The two muscle groups work in opposition, so injection planning has to balance the whole forehead. Don't buy “one point” without knowing which muscle that point covers.

What causes forehead wrinkles?

1. Repeated brow raising and facial expression

The frontalis is the main muscle that raises the brows. Every time you're surprised, concentrate, or try to open your eyes wide, the skin folds into horizontal lines. People with strong muscles or very animated faces may see lines earlier than others their age.

2. Using the forehead to compensate for low brows or heavy upper eyelids

Some people don't raise their brows out of habit. Their body uses the frontalis to lift the brows and open the field of vision. Try relaxing your forehead and see whether your eyelids feel heavier or your brows clearly drop. If so, a doctor needs to assess the brows, eyelids and how both sides work before injecting.

A randomized study comparing forehead injection patterns found that different injection placements affect both line reduction and brow position. Injecting lower tended to drop the brow more than higher placements [3]. So there's no single injection plan that suits every face.

3. Age and skin changes

With age, collagen production falls, elastic fibers change and skin takes longer to spring back after folding. Dynamic lines gradually turn into static ones more easily. But “age” doesn't mean you have to treat them. The decision depends on your concerns, your health and what suits you.

4. Sun exposure

UVA and UVB contribute to photoaging, including lines, rough skin and uneven color. A randomized trial following 903 adults for 4.5 years found that those who used sunscreen regularly showed less increase in signs of skin aging than those who used it at their discretion [4]. Sunscreen is the foundation of prevention, even though it can't relax the muscle that makes the lines.

5. Genetics and facial structure

Forehead height, brow position, skin thickness, eye socket shape and muscle strength all vary with genetics. Some people have forehead lines from a young age without any disease or abnormal skin damage.

6. Smoking, pollution and habits

Smoking is linked to skin aging and poorer healing. Poor sleep or dehydrated skin can make you look tired and make shallow lines more obvious for a while. But drinking more water or sleeping more won't erase deep lines driven by muscle and structure.

7. Changes in volume and bone

In some deep lines, the tissue under the skin and the bone beneath contribute to a hollow. But the forehead has blood vessels that connect to the area around the eyes, so any filler needs a clear reason and a higher level of risk assessment than simply thinking of it as “a groove to fill in”.

Forehead wrinkles at a young age: is that abnormal?

Mostly, no. Lines can come from strong muscles, frequent brow raising, low brows, heavy upper eyelids, dry skin, sun or genetics. Before assuming you need injections to prevent them, ask whether the lines show with your face still or only when you move, and how much they actually bother you.

The idea that you must start injections young so you never get lines isn't right for everyone. Preventive treatment should have an indication, use a sensible amount, and not reduce the movement you still need to lift your brows.

A first check of your forehead line type

Face the camera in natural light and take three photos at the same distance: relaxed, brows raised and frowning. Use the table below to prepare questions for your doctor. It doesn't replace an examination.

What you see	Main cause to assess	Approach often considered
Horizontal lines only when you raise your brows	Frontalis activity	Botulinum toxin that preserves appropriate movement, or no treatment yet
Lines remain at rest, but shallow	Muscle plus skin aging	Botulinum toxin plus sunscreen, retinoids or skin procedures as indicated
Deep grooves even when the muscle is relaxed	Deep static lines; volume or fibrous tissue involved	Control muscle force first, then assess resurfacing, or filler in selected people who accept the risk
You need to raise your brows to feel your eyes open comfortably	Frontalis compensating for low brows or heavy eyelids	Assess brows and eyelids before injecting; may need a plan that conserves lift, or referral to a surgeon
Fine lines all over the forehead	Dry, rough or sun-spotted skin; barrier and photoaging	Moisturizer, sunscreen, retinoids, laser or resurfacing depending on skin tone
Vertical lines between the brows	Corrugator / procerus	Assess the glabellar complex separately from the frontalis
Sudden asymmetry or drooping eyelid	Possibly neurological, not a wrinkle	Urgent assessment, especially with weakness in an arm or leg or slurred speech

How to reduce forehead wrinkles: choosing by cause

1. Sunscreen and skincare: the base for every type of line

Home care reduces the factors that age the skin and makes shallow lines look softer, but it can't stop the frontalis the way an injection does.

Sunscreen: choose a broad-spectrum one you'll actually use every day, apply a sensible amount and reapply outdoors. A hat and avoiding strong midday sun help too.

Moisturizer: reduces water loss and plumps the skin for a while, so fine lines look softer. It doesn't build deep collagen right away.

Retinoids: randomized trials and reviews of trials found tretinoin helps photoaging and lines when used consistently [5]. It can cause dryness, stinging and peeling and irritate easily, so start as an expert advises. People who are pregnant or planning to be should avoid retinoids and ask a doctor.

Vitamin C, peptides and antioxidants: may be a useful add-on to a routine, but formulas, concentrations and stability vary, and the evidence and size of effect aren't equal to a medication that's been studied. Don't expect them to erase deep lines in a few days.

2. Botulinum toxin: the main option for dynamic forehead lines

Botulinum toxin type A reduces release of acetylcholine at the junction between nerve and muscle, temporarily lowering the force of contraction. When the frontalis folds the skin less, lines when you raise your brows soften, and static lines may not be folded as constantly. For the mechanism and an overview, read about what Botox is.

A randomized Phase 3 study found onabotulinumtoxinA gave clearly greater improvement in moderate to severe forehead lines than placebo at day 30 [2]. But the results for one brand shouldn't be used for every product, and the “units” of each botulinum toxin brand can't be directly compared or converted. The current BOTOX Cosmetic label says so explicitly [1].

When it starts working: you generally notice less movement within several days, and results are fairly settled at about 2 weeks. Effects are temporary and usually fade gradually over several months. Actual duration depends on the product, dose, muscle, metabolism and your treatment history. More on this in how many days Botox takes to work.

A good goal: reduce the folding force while leaving the movement that suits your expressions and helps lift your brows. It isn't necessary to make everyone's forehead completely still.

Why can forehead injections drop the brow or make eyes feel heavy?

The frontalis is the brow-lifting muscle. If the drug spreads into the parts that hold the brow up, or the dose is too high for your muscle strength, the brow can drop, especially in people who were already using the forehead to compensate for heavy eyelids.

The 2024 BOTOX Cosmetic label reports, from trials treating forehead and frown lines together, headache in 9%, eyelid ptosis in 2% and brow ptosis in 2% of people receiving the drug [1]. Those figures belong to that formulation, dose and trial. They aren't the rate for every brand or technique, but they confirm brow drop is a real risk to explain before treatment.

Assessment before injecting should include:

• Brow position at rest, and when gently closing the eyes
• Whether the upper eyelids have excess skin, or the muscle that lifts the lid is weak
• Forehead height and how the frontalis works
• Any existing difference between left and right
• Whether you've had eye surgery, a brow lift or earlier injections
• How much brow-raising and facial expression you want to keep

For location-specific details, see our guide to Botox for the forehead.

3. Resurfacing laser, microneedling and chemical peels

These target the skin more than the muscle. They suit static fine lines, rough texture, pores or photoaging, depending on the device.

• Fractional ablative laser: creates controlled micro-wounds to stimulate repair. It affects texture more clearly but comes with downtime and a higher risk of post-inflammatory dark marks, especially in Asian skin if the energy isn't set appropriately.
• Non-ablative fractional laser: less downtime, but usually needs several sessions, and does less for deep grooves.
• Microneedling or RF microneedling: uses needles to make tiny channels or deliver energy into the skin. It may help texture and firmness. Raised scarring, infection and skin tone have to be assessed.
• Chemical peels: work on superficial to deep layers depending on the acid, strength and contact time. Don't do strong acids at home.

None of these directly reduces frontalis force. If the lines are being folded over and over, results on the skin may be limited or the lines may come back quickly, so a plan may combine them with a measured amount of muscle control.

4. Ultrasound or radiofrequency lifting

Ultrasound and radiofrequency energy heats tissue in a controlled way to stimulate collagen remodeling. It suits cases where there's also some laxity or skin-quality decline. Results are gradual and typically mild to moderate. It doesn't replace botulinum toxin for lines clearly caused by brow raising.

People with low brows may benefit from planning lifting in certain areas, but results depend on anatomy and the device, and no one should promise how many millimeters a brow will lift. One example technology on the Vanish Clinic website is Ultraformer III. For skin-quality approaches, read more on stimulating collagen in the face.

5. Filler for deep forehead grooves: only in selected people, with an extra-careful risk discussion

Deep static grooves may remain even when the muscle is relaxed. Some doctors consider a small amount of HA filler in selected cases. But the forehead has blood vessels that connect with the vessels around the eyes, and a blockage could lead to skin death, abnormal vision, blindness or stroke.

The US FDA states that injecting dermal filler in the forehead is an unapproved use in the US, and warns about injection into blood vessels [6]. Approved uses in Thailand have to be checked against the product and its current label. Don't assume every filler brand can be used in the forehead.

If you're considering this, ask why botulinum toxin and skin resurfacing aren't enough, whether the extra benefit from filler is worth the risk, which product is used, what the plan is for vascular occlusion, and how fast the clinic can refer you to emergency eye care. For the basics on fillers, read what filler is.

6. Brow lift or eyelid surgery for people who compensate with the forehead

If the main problem is a low brow or excess upper eyelid skin, injecting only the forehead may not fix the cause and may make you feel heavier. People whose field of vision is affected, or who use the frontalis all the time, should be assessed by a doctor who looks at the brows, eyelids and vision together. Surgery involves incisions, recovery and risk, so it isn't for everyone, but it's worth discussing honestly when non-surgical procedures don't do enough.

Comparing ways to treat forehead wrinkles

Method	Best for	Starts to show	Strength	Key limits and risks
Sunscreen + moisturizer	Everyone, especially dry or photoaged skin	Hydration quickly; anti-aging effect needs consistency	Prevents damage and supports the skin barrier	Doesn't reduce muscle force or erase deep lines
Retinoids as indicated	Shallow lines and sun-affected skin	Weeks to months	Evidence for photoaging	Dryness, stinging, peeling. Avoid in pregnancy; match to your skin
Botulinum toxin	Dynamic lines, and static lines where muscle force is dominant	Starts within days; assess at about 2 weeks	Targets the muscle cause	Bruising, headache, asymmetry, brow or eyelid droop. Temporary, and rarely, toxin spread
Laser / peel / microneedling	Static fine lines, rough texture, sun spots	Weeks, and may need several sessions	Improves skin quality	Irritation, wounds, infection, dark marks or uneven color. Limited effect on muscle
Ultrasound / RF	Laxity or skin-quality decline alongside	Gradual over weeks to months	No filler material	Lift is usually modest; pain, swelling, burns or fat-layer changes if used wrongly
HA filler	Deep static grooves in selected people	Initial change once swelling settles	Can fill a hollow	The forehead is a high-risk area for vessels and vision. Not a general first-line option
Brow / eyelid surgery	Low brow, excess eyelid skin or heavy frontalis compensation	After wounds and swelling heal	Treats the structural cause in suitable people	Surgery, recovery and surgical risk

How many units of Botox for the forehead?

There's no single number that is safe and looks good on everyone. The dose depends on the brand and formulation, because the units of each botulinum toxin product can't be directly compared or converted [1]. It also depends on forehead height, muscle strength, brow position, eyelids, sex, age group, lines at rest and the result you want.

The US label for onabotulinumtoxinA has a dosing plan for forehead lines together with frown lines that was studied, but that figure isn't a recipe for patients to ask for, and it can't be substituted for another brand. A doctor should explain which muscles are being treated, why they're being treated together, or why they chose to keep some force.

Choosing on “cheapest per unit” without knowing the source, dilution, storage and who injects raises the risk of both poor results and complications.

What should results look like, and how long do they last?

A reasonable result is softer lines when you raise your brows, possibly shallower lines at rest, and a face that can still express emotion. When the drug wears off, movement gradually returns. That doesn't automatically mean the lines “bounce back worse”, though the skin still changes with age and sun.

Duration is generally measured in several months, and no one should guarantee an end date. People with strong muscles, who exercise a lot, or who chose an expression-preserving dose may feel movement return sooner. Re-injecting more often than needed adds cost and may raise the chance of a weaker response over time, so wait for the review the doctor schedules.

Side effects after forehead injections

Common and usually temporary

• Needle marks, mild swelling, tenderness or bruising
• Headache or a tight feeling
• The two sides responding unequally at first
• A change in brow shape, or some lines remaining in certain spots

Don't rush to top up before your review. Each point starts working at a different time, and correcting too early can leave you with too much once the drug takes full effect.

Situations where you should contact your doctor

• A dropped brow or eyelid that interferes with vision
• Dry or burning eyes, being unable to close your eyes fully, or double vision
• Clear asymmetry once the review period has passed
• A rash, hives, unusual swelling or suspected infection

Emergency symptoms

Botulinum toxin labels carry a boxed warning that the effects of the toxin can spread away from the injection site. Dangerous symptoms include difficulty swallowing, speaking or breathing, generalized muscle weakness or double vision, and need treatment immediately [1].

If your face or the corner of your mouth droops, your arm or leg becomes weak or numb, your speech becomes slurred or you lose balance suddenly, think of stroke and call 1669. Thailand's Department of Disease Control recommends the F.A.S.T. rule: Face, Arm, Speech and Time [8].

Who should not have injections, or should wait

Contraindications on the onabotulinumtoxinA label include a history of allergy to botulinum toxin or its ingredients, and an infection at the injection site [1]. These groups should tell their doctor and be assessed specially:

• Pregnant, breastfeeding or planning a pregnancy, because it's elective and safety data are insufficient
• Neuromuscular conditions such as myasthenia gravis or Lambert-Eaton syndrome
• Existing difficulty swallowing or breathing, or muscle weakness
• Drooping eyelids or brows, very dry eyes, or a history of complications from injections
• Taking medicines that interfere with nerve-muscle signaling, such as aminoglycoside antibiotics or muscle relaxants. Tell your doctor and never stop the medicine yourself
• Fever, inflamed acne, cold sores, a rash or a wound on the forehead
• Taking anticoagulants or antiplatelet drugs, which may make bruising easier. Never stop prescribed medication yourself
• Recent botulinum toxin of another brand. Give the date, area and amount as far as you know

What should you ask your doctor before injections?

1. Are my lines dynamic, static, or mixed with sun-damaged skin, and how much of each?
2. Do I use my frontalis to lift my brows or eyelids, and how likely am I to feel heavy-eyed?
3. What product is it, what is it registered for, and how can I check it's genuine?
4. Which movement will you keep, and how much improvement do you expect in my lines at rest?
5. If a groove remains after 2 weeks, is the next step to wait, add carefully, or work on the skin rather than automatically adding more?
6. If my brow or eyelid drops, or something unusual happens, who can I contact throughout the period afterward?

Check the product and label using the guidance on how to check Botox is genuine, and check the injector's license with the Medical Council.

Aftercare after forehead injections

Follow your doctor's advice and the product documents above all. The general guidance is not to press, massage or rub the injection points early on, to keep the area clean and to avoid activities that bump the area right away. If bruising appears, use the method your doctor recommends.

Don't stop your regular medication yourself, don't buy medicine or inject a correction from another source, and don't assume that going into a sauna or eating certain foods will dissolve the drug immediately. The evidence behind many online prohibitions is uneven, so follow advice specific to the product and your actual symptoms. More on this in Botox aftercare.

Attend the review the doctor sets, usually about 2 weeks before judging the full result. Take photos in the same light and with the same expressions to compare, which reduces errors from camera angle.

Can you combine Botox with lasers or lifting devices?

In some plans, yes, because each method treats a different layer. But order and spacing depend on the type of device, the heat, how deep the skin is treated, the risk of swelling and the product's policy. Don't assume everything can be done on the same day.

The principle is that each method has one clear job: botulinum toxin lowers folding force, laser works on skin, an energy device works on laxity, and they're sequenced so you can tell whether each adds real benefit. Doing several things at once without a baseline makes it impossible to tell what worked or what caused a problem.

Doctor Insight

Before reducing forehead muscle force, check whether the patient is using the forehead to lift the brows or open the eyes. If relaxing the frontalis leaves the brows low or the eyelids heavy, the plan should conserve more lift, or the brow and eyelid structure should be assessed too. The goal isn't the stillest forehead. It's lower line depth without trading it for heavy eyes, a stiff expression or a brow shape that doesn't suit the face.

Forehead wrinkles: frequently asked questions

Can I treat forehead wrinkles without injections?

Shallow lines from dry skin and sun can improve with moisturizer, sunscreen and retinoids as indicated. Static lines may improve with laser or resurfacing. But lines driven by a strong frontalis will still fold when you raise your brows, because these methods don't reduce muscle force.

Do creams really reduce forehead wrinkles?

Hydrating creams make shallow lines look softer, and tretinoin has evidence against photoaging when used consistently. But no cream works like botulinum toxin or fills a deep groove instantly. Treat the claim “results like an injection” with care.

Do forehead patches help?

They may limit movement or smooth the skin for a while as long as they're on, but evidence for changing deep lines over the long term is limited. The adhesive can irritate, so people with sensitive skin should test first and not use them on inflamed skin.

Does forehead Botox make your face feel tight or frozen?

It can if movement is reduced more than intended. Assessing muscle strength and aiming to preserve expression lowers the chance, but it can't guarantee the same feel or shape for everyone.

Will forehead injections drop everyone's brows?

No, but it's a real risk, especially for people with low brows, heavy eyelids, forehead compensation, or a placement and dose that don't suit them. Examining at rest and in motion matters more than a fixed injection-point plan.

How many days does forehead Botox take to work?

You usually notice it within several days and see close to the full effect around 1 to 2 weeks, though products and people differ. Don't rush to top up before your review.

How many months does forehead Botox last?

It's generally temporary, lasting several months. Actual duration depends on the product, dose, muscle and your biology. Don't expect a guaranteed 4 or 6 months for everyone. If results are unusually short, check the product, technique, spacing and other causes before concluding you've become “resistant”.

Does frequent injection make you resistant to Botox?

The body can form neutralizing antibodies, but that isn't the only reason for a weak result. Frequent treatment, cumulative dose, the product, storage, the muscle or judging too early can all play a part. Space treatments as your doctor advises and avoid frequent small top-ups without need.

How is filler different from forehead Botox?

Botulinum toxin reduces muscle force, so it suits dynamic lines. Filler adds volume, so it might be used for some static grooves, but the forehead is a high-risk area for blood vessels and the eyes. Filler isn't a substitute for Botox and shouldn't be chosen just because you want a groove gone instantly.

Can HIFU or RF help forehead wrinkles?

They may help firmness and some degrees of laxity, but their effect on lines caused directly by the frontalis is limited. If your brows are low, take care over placement and ask whether the small lift that's possible meets your goal.

Are forehead wrinkles linked to stress?

Stress may lead you to frown, sleep less or look after your skin less, so lines look more obvious indirectly. But you can't diagnose someone's state of mind from the number of lines on their forehead, and reducing stress won't erase structural lines.

How much does forehead Botox cost?

Price depends on the product, the dose, other areas treated together, the doctor's expertise and the aftercare system. Don't compare only baht per unit, because units from different brands can't be compared directly, and an unusually low price may reflect a product of unknown origin. See Botox price and what makes it vary.

What age should I start treating forehead wrinkles?

There's no age everyone must start. Treatment should be based on your actual lines, how your brows work, your health, your wishes and your understanding of the risks, not because a friend or social media says to prevent before a certain age.

How to choose a clinic for forehead wrinkles

Choose a licensed facility where a doctor examines your brows, eyelids and movement before suggesting a number of units, opens the box and shows the label, takes standard photos, books a review and offers a channel for care if you get a dropped brow, a drooping eyelid or anything unusual.

Be wary of places that sell injection points without looking at your actual face, guarantee your brows definitely won't drop, claim that units are equal across every brand, or push you to top up before the review window is over. You can look at the Vanish Clinic doctors' profiles and check the practitioner's name in the Medical Council database before you decide.

Summary: separate muscle, skin and structure before treating forehead wrinkles

Dynamic lines usually respond to botulinum toxin, while static lines need skin quality and deep grooves considered as well. Sunscreen and skincare are the foundation. Laser or skin procedures help texture, an energy device has a role when there's laxity, filler is only for selected cases because the forehead is a high-risk area, and people who use the frontalis to compensate for their brows or eyelids may need structural assessment first.

The goal isn't to erase every line. It's a relaxed face that keeps brow lift, eye opening and natural expression. Assessing you at rest, raising your brows, frowning and with eyes gently closed makes for a plan that's safer and matched to the cause, more than choosing by number of units or a promotion.

Medical disclaimer

This article is general information. It does not replace an examination, diagnosis or personal advice. Results and risks vary with anatomy, health conditions, the product, the device and who performs the procedure. If you have difficulty swallowing, speaking or breathing, muscle weakness, double vision, or a drooping face with weakness in an arm or leg or slurred speech, go to a hospital or call 1669 immediately.

References

U.S. National Library of Medicine, DailyMed. BOTOX Cosmetic (onabotulinumtoxinA) Prescribing Information, revised 10/2024. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=485d9b71-6881-42c5-a620-a4360c7192ab

De Boulle K, et al. Forehead Line Treatment With OnabotulinumtoxinA in Subjects With Forehead and Glabellar Facial Rhytids: A Phase 3 Study. Dermatol Surg. https://pubmed.ncbi.nlm.nih.gov/33065953/

Cotofana S, et al. The Impact of Upper Face Botulinum Toxin Injections on Eyebrow Height and Forehead Lines: A Randomized Controlled Trial and an Algorithmic Approach to Forehead Injection. Plast Reconstr Surg. 2018. https://pubmed.ncbi.nlm.nih.gov/30102667/

Hughes MCB, et al. Sunscreen and prevention of skin aging: a randomized trial. Ann Intern Med. 2013. https://pubmed.ncbi.nlm.nih.gov/23732711/

Griffiths CEM, et al. Treatment of photodamaged facial skin with topical tretinoin. N Engl J Med. 1989. https://pubmed.ncbi.nlm.nih.gov/2674225/ and Sitohang IBS, et al. Topical tretinoin for treating photoaging: A systematic review of randomized controlled trials. https://pubmed.ncbi.nlm.nih.gov/35620028/

U.S. Food and Drug Administration. Dermal Fillers (Soft Tissue Fillers). https://www.fda.gov/medical-devices/aesthetic-cosmetic-devices/dermal-fillers-soft-tissue-fillers

American Academy of Dermatology. Wrinkles: Diagnosis and treatment. https://www.aad.org/public/cosmetic/wrinkles

Department of Disease Control (Thailand). Stroke warning signs: F.A.S.T. https://ddc.moph.go.th/odpc5/news.php?deptcode=odpc5&news=35415