Serum Before or After Red Light Therapy? What the Science Says About Timing, Formula Type, and LED Compatibility

Use serum after red light therapy unless the instructions for your exact device permit the specific topical product before treatment. If the device calls for clean, dry skin, follow that instruction. Neither a water-based serum nor an oil-based red light therapy serum is required to “activate” the light, and an ingredient list cannot prove improved light penetration.

Elora Clinic offers a water-based Green Tea Face Serum for lightweight hydration and an oil-based Red Light Therapy Serum for emollience and slip. Either may fit a comfortable post-session routine. Their different textures do not establish device compatibility or clinical enhancement.

Green Tea Face Serum cartons from Elora Clinic

In this article

Serum Before or After Red Light Therapy: The Direct Answer
Red Light Therapy Does Not Need a Serum to “Activate” It
Four Red-Light Variables Matter Before We Even Discuss Serum
What Changes When Serum Is Applied Before the Light?
Elora Clinic Water-Based vs. Oil-Based Red Light Therapy Serums
What the Green Tea Research Does—and Does Not—Show
Device Type Changes the Answer
Choose Skincare by Comfort and Purpose
Practical Routines Before and After LED
Safety: Stop a Reaction Rather Than Merely Changing the Order
How to Read Claims About LED Serums
Common Questions
Founder and Formulation Perspective
Final Takeaway: Serum Before or After Red Light Therapy?

Serum Before or After Red Light Therapy: The Direct Answer

Situation	Practical choice
Device says clean, dry skin	Cleanse and dry skin before the session; apply tolerated skincare afterward.
Device permits a named serum or medium	Use that specified product and amount. Permission for one formula is not permission for every serum.
Instructions do not address your serum	Ask the manufacturer or keep the serum for afterward.
Product or device causes burning, rash, or pain	Stop the offending product or session; changing the order is not a remedy for a reaction.

As one example, Omnilux’s quick-start guidance describes preparation and its own optional hydrogel. That is device-specific guidance, not evidence that all water serums or facial oils can be used underneath every LED mask. Keep the instructions supplied with your model as the deciding source.

Red Light Therapy Does Not Need a Serum to “Activate” It

Photobiomodulation, often abbreviated PBM, is produced by the light emitted from the device.

A topical serum is not required to turn that process on.

Red and near-infrared photons interact with biological tissue and can initiate cellular signaling through mechanisms that continue to be studied.

Commonly discussed pathways include:

mitochondrial photoreceptors,
cytochrome c oxidase,
changes in ATP-related activity,
reactive oxygen species signaling,
calcium signaling,
transcription-factor activity,
and downstream tissue responses.

The exact biological response depends on multiple variables.

Among the most important are:

wavelength,
irradiance,
fluence,
exposure time,
treatment frequency,
distance from the device,
and the tissue being treated.

A serum cannot replace those physical parameters.

This is why phrases such as “activation serum” need careful interpretation.

A serum may support the skincare routine around PBM, but the light source itself creates the photobiological stimulus.

Four Red-Light Variables Matter Before We Even Discuss Serum

1. Wavelength

Wavelength describes the spectral region of the emitted light.

Many consumer red-light devices use wavelengths near:

630 nm,
633 nm,
650 nm,
or 660 nm.

Near-infrared systems may incorporate wavelengths such as:

810 nm,
830 nm,
or 850 nm.

Different wavelengths interact differently with biological tissue because absorption and scattering are wavelength-dependent.

That already tells us something important:

A statement about what a serum does at 633 nm cannot automatically be applied to 850 nm.

2. Irradiance

Irradiance describes optical power reaching a unit area.

It is commonly expressed as:

mW/cm²

Two devices can emit similar wavelengths while delivering substantially different irradiance.

That difference can influence the treatment dose considerably.

3. Fluence

Fluence, or radiant exposure, describes the total energy delivered per unit area.

It is commonly expressed as:

J/cm²

In a simplified system:

Fluence = Irradiance × Time

Real devices can be more complicated because geometry, pulsing, distance, and beam distribution may influence actual exposure.

Still, this relationship illustrates why simply increasing treatment time changes dose.

4. Distance and Treatment Geometry

A device sitting against the face is different from a panel positioned several inches away.

Emitter-to-skin distance can influence:

irradiance,
treatment uniformity,
coverage,
and angle.

Mask shape can also create different distances across the:

forehead,
cheeks,
nose,
chin,
and jaw.

This matters because serum is only one variable in the system.

Correct device positioning may influence treatment conditions much more strongly than the presence of a tiny amount of serum.

More Red Light Is Not Automatically Better

Photobiomodulation does not necessarily follow the rule:

more energy = more benefit

PBM research frequently discusses a biphasic dose response.

In simplified terms, an insufficient dose may produce little effect.

An appropriate dose may produce the desired biological response.

Excessive exposure does not necessarily continue increasing that response and may produce diminished effects under some experimental conditions.

Therefore, serum choice cannot rescue a poorly designed treatment protocol.

A perfectly formulated skincare product cannot compensate for:

the wrong device distance,
excessive treatment duration,
inappropriate frequency,
or inadequate irradiance.

The dose at the skin depends on the device and setup. Do not extend sessions or move closer to compensate for an untested serum layer. A calculated fluence is not a personalized treatment recommendation.

What Changes When Serum Is Applied Before the Light?

Clear Does Not Mean Optically Invisible

A serum may look completely clear to the human eye.

That only tells us something about how it interacts with wavelengths within the visible spectrum strongly enough for us to perceive.

It does not tell us its exact:

absorbance at 633 nm,
transmission at 660 nm,
reflectance at 830 nm,
or behavior at 850 nm.

Those values would need to be measured.

Likewise, a lightly colored botanical serum is not automatically incompatible with red light.

The relevant question is:

How does the finished formulation interact with the particular wavelength emitted by the device?

How a Film Can Interact With Light

Optical event	What happens	Why it matters before red light
Reflection	Light returns away from the surface	Some incident energy may not enter the skin
Refraction	Light changes direction crossing between materials	Surface interfaces can change the light path
Absorption	Molecules absorb photon energy	Less light may continue through the film at that wavelength
Scattering	Light changes direction repeatedly	Distribution of light in tissue may change
Transmission	Light passes through the material	Determines how much continues toward the skin

This is why the phrase:

“This serum helps red light penetrate”

is scientifically much stronger than it sounds.

To make that claim convincingly, the finished product should actually be tested.

What Would a Serious Serum Transmission Test Measure?

A rigorous experiment could evaluate the finished serum at wavelengths relevant to common PBM devices.

For example:

630 nm,
633 nm,
660 nm,
810 nm,
830 nm,
850 nm.

Researchers could measure:

spectral transmittance,
absorbance,
reflectance,
scattering behavior,
refractive index,
and the effect of film thickness.

Testing several application amounts would be particularly useful.

A thin serum film may behave differently from a thick wet layer of the exact same formulation.

That is why product quantity matters before LED.

Why Film Thickness Is an Underrated Variable

Imagine using one drop of serum across the entire face.

Now imagine applying six pumps until the skin looks visibly wet.

The ingredient list has not changed.

The optical path has.

A thicker film creates more material through which light must travel.

Depending on the formula, that may affect:

absorption,
reflection,
scattering,
surface uniformity,
and device contact.

Mechanically, excess serum can also make a mask:

slide,
lift away from certain areas,
or sit differently across facial contours.

Therefore, a serum that works perfectly well as a thin pre-treatment layer may behave very differently when heavily applied.

Why Clean, Dry Skin Is Such a Strong Scientific Baseline

Bare skin reduces variables.

The routine becomes:

Cleanse → dry → red light therapy → skincare

For users starting a new LED device, this sequence has several advantages.

It makes it easier to determine:

how the device itself feels,
whether redness is caused by the device,
whether treatment warmth is comfortable,
and how the skin responds without topical interference.

That is also why device instructions deserve priority over generic advice found online.

If a manufacturer tested and designed its device for clean, dry skin, introducing an untested topical layer creates another variable.

Can Oil Block Red Light?

The statement “oil blocks red light” is too simplistic.

Optical behavior depends on:

the exact oil composition,
wavelength,
absorption spectrum,
scattering,
refractive index,
and film thickness.

A very thin transparent oil film is not physically equivalent to a thick opaque cream.

However, visual transparency also does not prove complete transmission.

If a company wants to claim that an oil formula transmits a particular percentage of 660-nm or 850-nm light, the finished product should be measured.

The scientifically responsible position is therefore:

Oil is neither universally forbidden before red light nor automatically proven to be optically neutral.

Device instructions and formulation-specific evidence should guide the decision.

Can a Water Serum Improve Red-Light Penetration?

The same caution applies here.

Water-based does not mean optically invisible.

A serum can contain:

botanical compounds,
humectants,
polymers,
electrolytes,
preservatives,
and other dissolved ingredients.

Each finished formulation has its own optical behavior.

Therefore, it would be inaccurate to claim that water-based skincare automatically improves PBM delivery.

The advantage of a thin water serum before LED is mostly practical:

faster dry-down,
lower surface slip,
easier mask positioning,
and lightweight hydration.

Those benefits are already meaningful without exaggerating the optics.

What Does “Light Penetration” Actually Mean?

The phrase “improves light penetration” is used casually online, but scientifically it is a specific claim.

Light entering the skin can be:

reflected,
absorbed,
scattered,
or transmitted deeper into tissue.

Red and near-infrared wavelengths generally penetrate more deeply than shorter visible wavelengths because biological chromophores absorb and scatter them differently.

However, penetration is not a fixed property of wavelength alone.

It also depends on tissue composition.

Skin contains:

water,
lipids,
melanin,
hemoglobin,
proteins,
extracellular matrix,
and cellular structures.

All of these can influence how light travels.

Adding a serum creates another optical medium at the surface.

The Air-to-Skin Interface Matters

When red light reaches untreated skin, photons transition from air into tissue.

Air and skin have different refractive indices.

Whenever light crosses between materials with different refractive indices, part of the light can be reflected.

A serum can change that surface interface.

That creates a theoretically interesting possibility:

If the serum has optical properties closer to those of superficial skin than air does, the surface reflection pattern may change.

But that does not automatically mean more therapeutically useful light reaches deeper tissue.

Why?

Because the serum may simultaneously:

absorb some wavelengths,
scatter light,
create an uneven film,
or alter device distance.

This is why refractive index by itself cannot prove that a serum improves PBM.

What Is Refractive Index?

Refractive index describes how light propagates through a material compared with a vacuum.

Different substances have different refractive indices.

Air is close to 1.

Water is higher.

Oils, glycerin, and biological tissues each have their own characteristic ranges.

When two neighboring materials have very different optical properties, reflection and refraction can occur at the boundary.

Matching those properties more closely can sometimes reduce surface mismatch.

This principle contributes to a field known as optical clearing.

Optical Clearing: The Science That Skincare Marketing Often Misuses

Optical clearing is a real area of biomedical optics.

Researchers have studied compounds such as:

glycerol,
propylene glycol,
polyethylene glycol,
sugars,
and other hyperosmotic agents

for their ability to alter tissue optical properties.

Under controlled experimental conditions, some optical-clearing agents can reduce scattering and improve visualization or light penetration within biological tissue.

That sounds extremely relevant to LED skincare.

But there is a major problem.

A cosmetic serum containing glycerin is not automatically an optical-clearing treatment.

Why Glycerin Research Does Not Prove That Every Glycerin Serum Enhances LED

Glycerin is one of the most common humectants in skincare.

It is also used in optical-clearing research.

Those two facts are often incorrectly combined into this claim:

“Glycerin improves light penetration, so glycerin serum makes red light therapy work better.”

That is not scientifically valid.

Optical-clearing studies may use:

much higher glycerol concentrations,
prolonged contact times,
specific tissue preparations,
controlled experimental conditions,
ex vivo tissues,
or specialized delivery methods.

A normal cosmetic serum may contain glycerin as only one component of a much larger formula.

The concentration may be very different.

Contact time may also be much shorter.

Therefore, the correct statement is:

Glycerin has genuine biomedical-optics relevance, but the presence of glycerin in a cosmetic serum does not prove that the finished product produces clinically meaningful optical clearing during LED therapy.

That distinction is crucial.

What Optical Clearing Actually Does

Biological tissue scatters light partly because of variations in refractive index between microscopic structures.

An optical-clearing agent may reduce some of those refractive-index differences.

Changes in tissue hydration can also alter:

collagen spacing,
interstitial fluid,
and tissue microstructure.

Under the right conditions, scattering can decrease.

When scattering decreases, light may travel differently through tissue.

But this process depends on:

concentration,
diffusion,
exposure time,
tissue type,
and agent chemistry.

This is much more complex than applying two drops of serum and turning on an LED mask.

Hydrated Skin Is Not Automatically Optically “Better”

Hydration is important for skin health.

Still, healthy hydration and optimal optical transmission are not synonymous.

Water itself has wavelength-dependent absorption.

Tissue hydration can alter both scattering and absorption.

At some wavelengths and conditions, hydration may influence optical behavior differently than expected.

Thus, a hydrating serum can be excellent skincare without needing a claim that it enhances photon delivery.

The Elora Clinic Green Tea Face Serum is a good example.

Its most defensible roles are:

hydration,
humectancy,
antioxidant support,
and providing a lightweight texture for compatible LED routines.

It does not need an unsupported claim of improved red-light penetration to be useful.

Why Color Matters

A serum can be visibly colored because of:

botanical extracts,
pigments,
oxidation,
active ingredients,
or other components.

Color means the formula interacts with at least some visible wavelengths.

However, visible color alone does not reveal the exact absorbance at 630, 660, 830, or 850 nm.

A green-tinted product may absorb strongly in some visible regions and weakly in others.

Brown botanical extracts can have broader absorption spectra.

Therefore:

“Looks clear”

and

“looks colored”

are only crude observations.

The correct measurement is wavelength-specific absorbance or transmittance.

Elora Clinic Water-Based vs. Oil-Based Red Light Therapy Serums

Water-based Green Tea Face Serum

The current Green Tea Face Serum lists water, aloe vera, glycerin, sodium hyaluronate, green tea extract, and formulation-supporting ingredients. It is a cosmetic hydration option. A thin-feeling or clear formula is not automatically optically neutral, and its label does not override your device manual.

Elora Clinic Green Tea Face Serum bottle and green carton

Oil-based Red Light Therapy Serum

The current oil serum lists squalane, avocado oil, sweet almond oil, black seed oil, green tea extract carried in hydrogenated vegetable oil, jojoba oil, and tocopherol. Its emollient texture can suit someone who enjoys a richer finish or facial massage. Check the full label for ingredients you avoid; botanical oils are not universally non-irritating.

Use oil before a device only when the manufacturer explicitly permits that type of product. Oil is not a substitute for the conductive or coupling gel required by some combination devices. After the session, use a small amount if it suits your skin; an oil is optional and may not replace your moisturizer.

Feature	Water-based serum	Oil-based serum
Primary cosmetic role	Lightweight hydration and skin conditioning	Emollience and lasting slip
Before illumination	Only within the device’s specific instructions	Only if oils are explicitly permitted
After illumination	Optional before heavier skincare	Optional later in the routine
Evidence needed to claim better LED results	Testing of the finished serum plus the device	Testing of the finished serum plus the device

What the Green Tea Research Does—and Does Not—Show

The 2009 report on green tea and 670 nm light described green-tea-soaked cotton pads before a particular light protocol. It was preliminary work, not a trial of either Elora Clinic serum or a comparison of modern consumer masks. It cannot establish faster results, improved penetration, or an ideal serum order for these products.

Antioxidants and PBM: A More Complicated Relationship

Red light therapy is sometimes described simply as “reducing oxidative stress.”

That description can be incomplete.

Photobiomodulation may involve transient changes in reactive oxygen species as signaling molecules.

Low-level ROS generation can participate in:

redox signaling,
transcription-factor activation,
cellular adaptation,
and downstream responses.

Antioxidants such as green tea polyphenols can influence oxidative biology.

This creates an interesting theoretical question:

Could topical antioxidant timing modify PBM-related redox signaling?

Possibly.

But that does not mean more antioxidants always produce better PBM.

Biological signaling depends on balance.

Why “More Antioxidants” Is Not a Scientific Rule

Reactive oxygen species are often portrayed as purely harmful.

In reality, ROS can be both:

damaging at excessive concentrations,
and useful signaling molecules at controlled concentrations.

Photobiomodulation appears to interact with redox biology partly through this signaling framework.

Therefore, claiming that a serum improves LED simply because it contains antioxidants is incomplete.

The exact effect depends on:

molecule,
concentration,
penetration,
timing,
cellular compartment,
and treatment dose.

This is one reason post-treatment antioxidant application can be especially logical.

It provides skincare support without requiring the assumption that the antioxidant must participate during the light exposure itself.

What Would Elora Clinic Need to Test to Make an Actual Optical Claim?

A scientifically meaningful testing program could evaluate both finished formulas.

For each serum, laboratory testing could assess:

spectral transmittance,
absorbance,
reflectance,
scattering behavior,
film thickness,
and optical changes over drying time.

Measurements could be performed at common PBM wavelengths such as:

630 nm,
633 nm,
660 nm,
810 nm,
830 nm,
850 nm.

That would allow questions such as:

Does the water-based serum meaningfully change transmittance at 660 nm?

Does a 10-micron oil film behave differently from a 50-micron film?

Does the serum’s dry-down change the result?

Does the green tea extract contribute measurable absorbance at the target wavelength?

Those are testable questions.

Why Optical Compatibility Is Not the Same as Clinical Enhancement

Suppose testing showed that a serum transmits 98% of 660-nm light through a standardized film.

That would be useful information.

It would suggest low attenuation in that test configuration.

It would not automatically prove that skin outcomes are better.

To establish clinical enhancement, researchers would need to compare actual biological or cosmetic outcomes.

For example:

Group 1

LED alone

Group 2

LED + water-based Green Tea Serum

Group 3

LED + oil-based Red Light Therapy Serum

Group 4

Serum alone

Group 5

Control

Researchers could assess:

hydration,
TEWL,
erythema,
elasticity,
wrinkle appearance,
standardized photography,
skin texture,
tolerability,
and potentially biological biomarkers.

Only then could a claim progress from:

“compatible with red light”

to something closer to:

“improves outcomes when paired with red light.”

That is a much higher evidence threshold.

Compatibility Is Still Valuable

A serum does not need to enhance PBM to be useful.

Compatibility itself can be meaningful.

A good red-light routine serum may:

maintain skin comfort,
fit the device correctly,
reduce unnecessary irritation,
provide hydration,
support the barrier,
improve routine adherence,
or provide post-treatment emollience.

Those benefits matter.

A person who dislikes the way their skin feels during or after LED may simply stop using the device consistently.

A serum that makes the routine more comfortable can therefore improve adherence even without changing photon biology.

Why Routine Adherence Matters More Than Theoretical Optimization

Photobiomodulation depends on repeated treatment according to an appropriate protocol.

Using the “perfect” serum once does not compensate for inconsistent device use.

Likewise, using an excellent device incorrectly can produce disappointing results.

The practical hierarchy should be:

Correct device.
Correct wavelength and protocol.
Correct treatment frequency.
Correct device positioning.
Comfortable, non-irritating skincare.
Serum timing optimized only after those fundamentals are established.

That hierarchy prevents skincare from distracting from the core PBM variables.

The trial groups above describe a possible study design, not a study Elora Clinic has performed. Compatibility means a product can be used as directed with a device; superiority requires a separate comparison of outcomes.

Device Type Changes the Answer

Close-Fitting LED Masks

Masks create the most complex pre-treatment environment.

They can:

trap moisture,
reduce evaporation,
create warmth,
press product against the skin,
shift if too much slip is present.

A thin water serum may be practical if the device manufacturer permits it.

Oil requires more caution because the surface may remain slippery longer.

Non-Contact LED Panels

Panels do not touch the face.

That removes some mechanical concerns.

There is no mask slipping.

Occlusion is also much lower.

However, the optical question remains.

Any serum applied before treatment still sits in the light path.

So a panel simplifies mechanical compatibility but does not eliminate optical uncertainty.

Handheld LED Devices

Handheld devices vary widely.

Some:

touch the skin,
glide across it,
or require a conductive or slip medium.

Others should be held slightly above the surface.

Therefore, serum choice must follow the individual device design.

An oil may be helpful for glide with one device and inappropriate for another.

Combination Devices

Some consumer tools combine LED with:

microcurrent,
radiofrequency,
vibration,
massage,
or heat.

Now the serum has more than one technical job.

For example, microcurrent devices may require a conductive medium.

Radiofrequency systems may need a compatible gel.

A red-light serum should never be assumed to substitute for those required media.

This is especially important because one device may contain multiple technologies that have different formulation requirements.

These are practical differences, not a compatibility chart. For every device category, follow its required skin preparation, eye protection, distance, timing, cleaning, and contraindications. A handheld device that glides on skin can still require a particular medium.

Choose Skincare by Comfort and Purpose

Skin type helps you choose post-session texture, but it does not change the device’s preparation requirements. For oily skin, a light moisturizer or serum may feel sufficient. Dry skin may prefer a cream; oil is an optional later step. Mature skin does not automatically need two serums. For actively irritated or unexplained inflamed skin, seek advice before adding a device session.

Hyaluronic acid, glycerin, niacinamide, vitamin C, and peptides do not have to be on the skin during illumination to serve their cosmetic purpose. No ingredient name alone establishes compatibility. Strong acids, retinoids, and benzoyl peroxide can already irritate; follow product, device, and prescriber instructions rather than putting them under a mask to seek extra benefit.

Related explanations remain available in our guides to hyaluronic acid and red light therapy, vitamin C and red light therapy, and green tea serum in an LED routine.

Practical Routines Before and After LED

A close-fitting mask

Cleanse → dry skin as instructed → complete the specified LED session → apply tolerated skincare. If using a water-based serum and an oil afterward, the lighter serum usually comes first. You do not need both. Keep enough slip off the mask to maintain the intended position.

A non-contact panel

Follow the specified distance and session time. A panel removes mask contact but does not remove the optical effect of a topical film. If the instructions do not support your chosen serum beforehand, apply it afterward.

A handheld or combination device

Use the exact medium required by the manufacturer. A red-light serum label does not establish electrical conductivity or radiofrequency coupling. Do not improvise with oil if the device requires a specific gel.

An established active-ingredient routine

Do not introduce LED and several new actives on the same day. Keep irritating products away from a session when instructions call for that, and ask your prescriber about prescribed actives. Separating a comfortable niacinamide step is straightforward; our newer niacinamide morning-or-night guide explains routine choices without requiring it during LED.

For a complete sequence, see how to build a red light therapy skincare routine. The red light therapy education hub brings together the related device and skincare questions.

Skincare liquid in a laboratory mixing vessel — Formulation photograph; it is not an optical transmission test.

Safety: Stop a Reaction Rather Than Merely Changing the Order

Stop using a serum that causes persistent burning, itching, increasing redness, swelling, or a rash. Rinse it off gently. Do not retry the same irritating product after LED as a workaround. If product migrates toward the eyes or the mask slips, stop the session and correct the setup before considering further use.

Stop the device if treatment causes painful heat, blistering, eye discomfort, or a significant reaction. Seek medical advice for severe or persistent symptoms. People with light-sensitive conditions or medicines that increase light sensitivity should ask a clinician before use. The AAD’s red light therapy guidance discusses safety, eye protection, and the limits of at-home treatment.

Serum is not a cooling system for an excessive light dose. Follow the recommended duration and schedule, and never increase exposure to “push through” a lack of visible results.

How to Read Claims About LED Serums

Claim	What would support it
Contains an ingredient	A current ingredient list.
Transmits light at a given wavelength	Optical measurements of the finished formula at a realistic applied thickness.
Works with a specific device	Device-specific compatibility and safety evidence.
Improves clinical results compared with LED alone	An appropriate comparative human study with defined outcomes.

Biological explanations are useful context, but they do not establish the performance of a finished serum. The same caution applies to terms such as “activation serum,” “optical clearing,” and “boosts penetration.” Our guide to red light activation-serum claims explains that distinction.

Common Questions

Does oil block all red light?

Not necessarily. Transmission depends on the finished formula, wavelength, film thickness, and setup. Neither “all oil blocks light” nor “all oil enhances light” is supported by the product category alone.

Can I use both Elora Clinic serums?

If both suit your skin, they can be optional steps after the session: water-based serum first, then a small amount of oil if needed. Using both has not been established to improve LED results and is not required.

Should a serum sting during LED?

No. Stinging is not a measure of effectiveness. Stop the product or treatment that causes discomfort and assess the cause; persistent or severe symptoms need professional advice.

Founder and Formulation Perspective

Elora Clinic separates the purpose of skincare from the purpose of the device: hydration and emollience are cosmetic functions, while the LED supplies light. Read about Elora Ellis and the brand’s formulation background or continue with red light therapy before or after skincare.

Final Takeaway: Serum Before or After Red Light Therapy?

Let the device instructions decide what goes on skin before treatment. Keep untested serums for afterward, select a comfortable texture, and stop products that irritate. A water-based serum and an oil serum can play different skincare roles without either being required to activate or improve LED.